Image by Steve Bidmead from Pixabay

I saw an answer on Quora the other week which related to the consequences of a 200-tonne asteroid made completely of gold crashing to Earth.

The answer dealt with the economic repercussions based on the resulting crash in the price of gold because the value attached to many commodities is a measure of their rarity.

This didn’t seem right to me, not completely anyway. It’s not rarity that causes the value of a commodity, it’s scarcity relative to demand.

Rarity is only half the story.

Rare Earth elements are both scarce and in great demand because they are essential to mobile phones and laptops and all sorts of other electronics due to their use in magnets and materials that respond to magnetic fields.

EE Doc Smith in the Skylark series made the point that platinum in quantity would posses engineering applications that would be a huge boon for mankind. Of course, he was largely making this stuff up off the top of his head, he could not know that platinum would one day be in equal demand for electronics as for jewelry, because it is a far better conductor (as are the other noble metals) of electricity. The smaller we make our digital devices, the greater the industrial demand for gold and platinum grows; already our computer chips are so tiny that their internal connections cannot be made of anything else or the chip would overheat and cease to function. Right now, gold is the preferred material, since it is more common (and hence helps keep the price of the chips down); but it is forecast that within a decade, platinum will be necessary.

Spices were once so valuable that they were traded as currency. But the reason they were valuable was that they were in demand – not only for the flavor contributions they could make, but to disguise the flavor and odors of meat that was going off but was still edible – and that the potential demand massively outstripped the available supply.

Purple is associated with royalty because the only really purple die available, named Tyrian Purple, used to be made exclusively in the Phoenician city of Tyre, in what is now Lebanon, from the ground up shells of a small mollusk that was exclusively found there. It took more than 9,000 such shells to create a single gram of the die – that’s 3-and-a-half hundredths of an ounce. Tyrian Purple died silk was literally worth it’s weight in gold. Purple die has only become available to the lower classes since 1856, when English chemist Henry Perkin accidentally created a synthetic purple that he patented and marketed under the name aniline purple – and earning himself a fortune in the process. (I’m always amused by cleric and mage robes being colored purple in illustrations, as a result of knowing this story. Many of them must have been wearing the value of their entire church or tower on their backs…). These days, that artificial color is known as Mauve, and the die is now commonly known as mauveine by chemists (Tyrian Purple was richer and darker in tone, more what we think of as the color of dark grapes).

But the poster-child for this principle is Salt. So essential to life that it was also traded as a currency, Salt is hardly rare – though salt from seawater contains dangerous impurities and needs to be refined before it is safe to consume. Again back in Phoenician times, its worth is now believed to have been equal to that of gold, by weight (though some historians are not certain of this). Salt’s value lay in its ability to preserve meat and fish; any value as a flavoring was secondary (though it is worth noting that pepper, which has no value except as a flavoring, has also been used as a currency). Some historians suggest that Roman soldiers were part-paid in salt, from which derives the old saying of people being “worth their salt”. So ubiquitous was the practice – in part due to the ultimate extent of the Roman Empire – that the word “Salary” actually derives from the Roman word for Salt.

The obvious world-building questions

There are some obvious questions that most established readers will expect me to raise at this point. Some of them would have occurred to almost anyone who’s reading this. Nevertheless, any given post is always some reader’s first, so it’s worth asking them explicitly, anyway:

  • What is valuable in your world that isn’t, or isn’t known, in ours?
  • Why is that commodity in demand? What’s it good for?
  • Who, in particular, wants it?
  • Where does it come from?
  • Who makes/mines/obtains it?
  • How is it obtained? Is that particularly difficult or dangerous to do, and why?
  • What has to be done to it to transform it into its valuable form?
  • Who has money and who doesn’t, as a result?
  • How much is this commodity worth?

I’ve highlighted that last question because it seems to be a critical question, and the only one that can’t reasonably be invented off the top of the GM’s head. It’s also the most complex question there, because the value has to reflect all the other answers and more besides.

But, before I get any further into that, it might be helpful to add to the state of confusion with one or two quick case studies.

Image by Tim C. Gundert from Pixabay, cropped, contrast enhanced, and background colors by Mike

A Confusion over Platinum

The impact of demand vs supply in terms of determining the value of a commodity is highlighted by the confusion over the value of platinum.

Supply first: Platinum is 16 times rarer than gold, and is found in nuggets of similar or smaller mass.

Specifying weights actually adds to the confusion experienced by most, simply because these elements are so heavy. A cubic cm of gold weighs 19.32 grams, and one of platinum weighs 21.42 grams. As a comparison, steel is approx 8 grams per cubic cm and water is 1 gram per cubic cm. To get oz per cubic inch, multiply by 1.73 to get gold=33.4, platinum=37, steel=approx 14, and water = 1.73 oz per cubic inch.

So a 12″ x 1″ x 1″ bar of steel would weigh about 168 oz, or a little over 10 lb. The same bar, if gold, would weigh 25.05 lb, and if platinum, 27.75 lb – the same as two-and-a-half of those iron bars (plus another quarter-bar for platinum).

Ten such bars are roughly 250lb and 280lb, respectively.

Saying that coins made of these, and other materials, are all approximately the same weight and size, makes zero sense until another word is introduced into the subject: adulteration. That’s the practice of mixing common or “base” materials – usually nickel, tin, or lead, or some combination thereof – into the coin material and then politely ignoring the fact.

According to D&D 3.x and 5e, 1 platinum coin is worth 10 gold pieces. From rarity alone, it should be 16, but maybe the presence of subterranean races has made platinum easier to find.

D&D 4e sets the value of platinum at 100 gold pieces.

As I write this, platinum is worth US$845.10 per oz, and gold, US$1222 per oz – in other words, platinum is 69% as valuable as gold.

Wait a minute – 69%, not 16 times? Or 10x? Or 100x?

The price of gold is clearly inflated by demand. Part of that demand is industrial, and part is economic – gold being the commodity in which most countries keep their treasury reserves. How big a factor is this demand?

Well, on rarity alone, if platinum is worth $845.10, gold should be worth one-sixteenth of that – $52.82 per oz. Instead, it’s worth more than 23 times as much.

Okay, so let’s assume adulteration, and use the straight rarity value since the only demands in fantasy times are coinage and jewelry. How much precious metal is actually in D&D coins?

This sort of calculation would be relatively easy if we specified the adulterating substance used – lead, say, or tin – and if the game rules didn’t specify that both size and weight were the same. But that fact means that the adulterated coins have the same density, and since gold and platinum weigh different amounts, and one is worth many times the other, that requires the adulterating material to be different in the two coins.

Let’s say (for the sake of argument) that the weight of both coins is 1.
Platinum is 16× the value of gold, so there’s only 1/16th as much precious metal by value in a platinum coin. So the other 15/16ths has to be something else – and gold is heavy. Not quite as heavy as platinum – and that means that the adulterating material has to be something just the right amount less dense than gold. Steel would be too light. We need something that’s 19.32 × (19.32 ÷ 21.42) = 17.42 grams per cubic centimeter in density. At 18.9, the closest match I can find is Uranium – no, I don’t think so. Next best would be a mixture of 26.4% lead and 73.6% tungsten (11.34 and 19.6, respectively). Except that Tungsten was only identified as a new element in 1781 and first isolated as a metal in 1783. Lead, of course, was well-known in Roman times, so that part of the formula, at least, is practical.

Of course, the magical coating of steel with Tungsten Carbide might be great explanation for plus-whatever weapons. So we can meet the rules specifications by stating that platinum coins are 69% ground-up plus-one weapons….

Copper Currency

Many nations used copper currency in the 19th and 20th century, including my native Australia. I still have a couple of US pennies from my visit there, as keepsakes. Inflation has killed off many of those coins; the price of producing the coins outstripping their value; the 1?ó and 2?ó coins were withdrawn from circulation in 1991, and the government has debated killing off 5?ó coins on a number of occasions in the 28 years since.

In medieval times, the time period upon which most fantasy and fantasy RPGs are based, copper currency was rare. Copper pieces did exist in some cultures, but were disliked or even despised by the commons.

In Britain, the common currency was based upon a pound of silver, (hence “pound sterling”) which was divided into 240 equal portions to create pennies. For smaller transactions, making change, etc. pennies were cut into halves (hence the “halfpenny”), quarters, sixteenths, or even (rarely) thirty-seconds.

The material of which these “copper coins” is made also makes them something of a misnomer in many places. Australian copper coins were actually 97% copper, 2.5% zinc, and 0.5% tin, which is pretty close to “truth in advertising” compared to other currencies.

Contrast that with the US 1?ó piece, which prior to 1982 was 95% copper and 5% tin & zinc – but which is now a zinc core comprising 97.5% of the coin and a copper plating comprising the remaining 2.5%. There is actually more copper in the nickel (75%) than in the modern US penny – and still more in the modern dime (91.67%).

Things aren’t much better across the pond: until 2008, the British penny had the same composition as Australian ‘copper’ coins (actually bronze). In 2008, the Brits shifted to copper plated steel. The ratios aren’t cited on Wikipedia, but we can guess from the US values – 97.5% steel, 2.5% copper.

At least with the more valuable coins, the precious metal incorporated constitutes a significantly greater value than the adulterating material – except, perhaps, in the case of platinum (see above). With copper coins, that ratio is quite likely to be very close to even.

True Value

But that brings me to a truth that stock market investors and economists understand very well – but few others appreciate: the value of a currency is whatever we agree that it is; it is more properly measured in terms of the work that it will do, i.e. its buying power.

When the US was on the gold standard, the value of a dollar was fixed – it was always worth so much gold. Floating the dollar was one of many measures undertaken by FDR to combat the Great Depression. From that time on, the value of a dollar depended on what it would buy you – when the material being bought is a foreign currency, it’s called an exchange rate. You can, in fact, estimate the value of the USD by the impact that its strength has on exchange rates – there was a period following the GFC in which Australian Dollars were at parity with the USD, or close to it, because Australia dodged the worst of that economic crisis through astute handling of our domestic economy and a timely stimulus response. These days, it’s back to being worth around 0.66-0.68?ó US to each AUD. This value changes depending on local economic conditions (boosts it if good, reduces it if bad) and the strength of the US Economy (reduces it if good, increases it if bad), so the exchange rate is a reasonable index for how the local economy is doing relative to the US standard. Since the 66?ó value is about what we expect, anything better means that Australia is doing well.

The same is true, in my book, for every price quoted in a source-book – this is the “theoretical” value of the item, i.e. what you would expect to pay for it. The reality on the ground might be very different.

Which reminds me of an episode of the West Wing, in which the President’s private secretary is considering the purchase of a new car, and it is revealed that she intends to pay the “Sticker Price” – even though that factors in room for the salesman to negotiate and is actually inflated above the true value of the car. Car salesmen expect to have to “do a deal” for less than the advertised price, in other words – a distinctive example of the difference between a “theoretical” value and the “true” value.

The Rarity Matrix

I’ve devised a fairly simple – some might say, oversimplified – system called the Rarity Matrix which makes it quick and easy for the GM to decide what the value of any commodity should be. This takes into account, in general terms, every essential factor that I could think of. What’s more, by noting the constituent measures that combine to define that value, a rich background for that commodity can be derived – one that goes a long way toward hinting at the answers to some of those other questions, or that can simply add to the plausibility and richness of the substance as an element of a campaign.

These are actually fairly easy to construct for yourself on scrap paper as needed – the following is just an example.
 

Rarity Matrix Scarcity Index
Demand Index 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3
– 1 -3 -2.75 -2.5 -2.25 -2 -1.75 -1.5 -1.25 -1 -0.75 -0.5 -0.25 0
– 0.75 -2.75 -2.5 -2.25 -2 -1.75 -1.5 -1.25 -1 -0.75 -0.5 -0.25 0 0.25
– 0.5 -2.5 -2.25 -2 -1.75 -1.5 -1.25 -1 -0.75 -0.5 -0.25 0 0.25 0.5
– 0.25 -2.25 -2 -1.75 -1.5 -1.25 -1 -0.75 -0.5 -0.25 0 0.25 0.5 0.75
0 -2 -1.75 -1.5 -1.25 -1 -0.75 -0.5 -0.25 0 0.25 0.5 0.75 1
0.25 -1.75 -1.5 -1.25 -1 -0.75 -0.5 -0.25 0 0.25 0.5 0.75 1 1.25
0.5 -1.5 -1.25 -1 -0.75 -0.5 -0.25 0 0.25 0.5 0.75 1 1.25 1.5
0.75 -1.25 -1 -0.75 -0.5 -0.25 0 0.25 0.5 0.75 1 1.25 1.5 1.75
1 -1 -0.75 -0.5 -0.25 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2
1.25 -0.75 -0.5 -0.25 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25
1.5 -0.5 -0.25 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5
1.75 -0.25 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75
2 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3
2.25 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3 3.25
2.5 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3 3.25 3.5
2.75 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3 3.25 3.5 3.75
3 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3 3.25 3.5 3.75 4

Before I get into meanings and usage, you should understand what the table content is and how was it derived. The value in any cell is the total of the row and the column index values, -2.
The only other thing that you have to do is pick a base value and a starting point on the table to represent that base value. I’ve picked index values of one and one, as you can see; which gives a value of zero in the table. This could represent 1 silver piece, 1 gold, or 100 gold; that’s up to you, the table doesn’t change with scale. (I was originally going to pick 2 and 2, but this choice gives more room for greater values).

The table can be extended indefinitely in any direction.

The Scarcity Index

The first step is to estimate the scarcity of the commodity to be valued relative to the base. Shift your column one to the right for each increase in rarity, or one to the left if the substance is more common than your base.

The first step covers materials that are 1.5x rarer; the second 3x rarer; the third, about 6x rarer; and every 4 steps is 10x rarer. These multiply – so to get about 16x rarer, it’s 4 steps + 1 step = 5 steps (10×1.5=15). That’s where we would find platinum, if gold was our basis.

    The Danger Shift

    Shift the column to the right to represent how much more dangerous it is to gather/acquire the material. Gold mining is a physically challenging task, with some danger involved, but it’s nowhere near as dangerous as diamond mining, for example. 1 step would be “just a little more dangerous”, 2 would be “significantly more dangerous”, and so on. Potentially, up to 8 steps could be made this way – gold mining vs stealing dragon scales from the original owner, for example. Once again, and in compound with scarcity, this can move you off the scale to the right or to the left.

    Note that the scarcity might already reflect, in whole or part, any possible danger shift. Don’t count it twice; isolate the two factors as best you can.

    The Scaling Shift

    The best way of shifting scales back to a value actually shown on the chart is to change units of measurement, a scaling shift.

    This is fairly easy with metric measurements – 12 steps to the right changes from grams to kilograms, 12 steps to the left from kilograms to grams. You don’t need to specify, because this also scales perfectly.

    It gets a little trickier with non-metric measurements (and there are rather too many of them to list here). So let’s pick a couple: Pounds to Ounces: There are 16 ounces in a pound, so that’s five steps to the left, while going in the other direction is five steps to the right. There are 14 pounds in a stone, so that’s also 5 steps. There are 143 stones in a tonne – so that’s 4+5=9 steps. Just reverse the direction to reverse the change in scale.

    Let’s be clear on what this says: the ultimate result is 1 [unit 2] of the material to be valued is worth so many times 1 [unit 1] of the base material. The two units start out with the same scale, lb for lb, oz for oz, and so on. So, with platinum, the scarcity shifts the value 5 columns to the left, but going from lb to oz shifts it back five columns to the left – so the comparison so far (assuming danger levels are about the same) is “1 oz of platinum = 1 lb of gold”.

    Tip: Another very useful attribute of the table: steps up are the same as steps left, and steps down are the same as steps right! That’s by virtue of using a consistent increase in both columns and rows, and one reason I did the table this way. It’s just too convenient a trick to ignore.

    Tip #2: It’s often advisable to leave this until last, or to perform only a partial adjustment at this point. Try to keep yourself to the middle of the chart, if you can, for maximum flexibility.

Image by Josch13 from Pixabay

The Demand Index

The other axis deals with the demand for the material. There are more possible shifting factors here, and some of them are a little more arbitrary. The first step is to estimate the level of base demand excluding the factors considered separately below – practical uses, superstition-based uses, use as a common currency, and official policies/laws regarding the material. These shifts are up or down (up indicating a reduced demand, down an increased demand).

Few materials will change very much, but one major factor that isn’t included on that list is portability. Spices, Salt, Rare Dies – these have all been worth their weight in gold, which gives them a high portability. If you use gold as your basis, then that doesn’t produce an automatic shift, but if the commodity being valued lacks that portability – lumber, for example – then steps up would be indicated.

    The Practicality Shift

    If there is a practical use to the material that no other material can satisfy, as shown by the analysis of gold price vs rarity, it can increase the value of a commodity by a factor of 24. This moves the demand down the page (i.e. increases it). 24 is more than 15, so we’re looking at 4+2=6 steps down the page for anything so extreme. Few materials are in such demand for practical applications in a fantasy/medieval culture.

    If there is a practical use to the material that no other material can satisfy quite as well, halve the number of steps. If there is a practical use that other materials can satisfy as well or better, subtract one or two from the halved total (two if possible) – just don’t decrease the demand to less than it was before making the practicality shift.

    The Superstition Shift

    Some cultures believe Rhinoceros Horn is an aphrodisiac. This causes them to be assigned huge value on the black market (because trade in them is illegal). Part of that value is due to the direct danger posed by hunting a very big and sometimes bad-tempered animal; part of it is due to the indirect danger of capture, prosecution, and imprisonment; and part is the value attached by this belief, regarded as superstition by most in the modern day. Well, the two danger components should be reflected in a Danger Shift (as described earlier); the rest belongs to a Superstition Shift.

    A Superstition Shift moves a value measurement downwards on the Demand Index, effectively increasing demand.

    1 space = +77.8% (or less)
    2 spaces = +216%
    3 spaces = +462%
    4 spaces = +900%
    5 spaces = +1678%

    The pattern of increase might not be immediately obvious, so let me point out that 900 + 778 = 1678, and 778 is ten times 77.8.

    Therefore, 6 spaces should be 10×216+900=+3060%.And, when I do the math, I get +3066% – close enough.

    The Economic Shift

    If a commodity is used as a medium of exchange, i.e. a currency, that automatically increases the desirability of that commodity. People who otherwise might not have wanted it, now have a perfectly legitimate reason to do so – and that group might outnumber those who would already have wanted it, quite substantially. This is reflected in an Economic Shift, usually down the table (increased demand).

    4 spaces = exclusive currency, meaning that no other medium of exchange is used by the society.
    3 spaces = one of a select group of currencies – the normal D&D/Pathfinder situation.
    2 spaces = a common currency used unofficially in addition to an official medium of exchange.
    1 space = an unusual/minor currency used unofficially in addition to an official medium of exchange.

    Of course, if the basis is a medium of exchange and the commodity is not, even if it could be, then the adjustment is in the other direction.

    The Incentive Shift

    I struggled to find a suitable name for this impact on demand and failed to find anything more suitable than “Incentive Shift”, which doesn’t really explain anything. So let’s try and clear up any confusion: from time to time, Governments have attempted to cultivate interest in developing/finding certain resources by declaring them tax-free or partially tax-exempt. This naturally encourages the citizenry who can afford to do so to convert some of their cash resources into the commodity, increasing demand for it. As more of the resource is found, assuming there is more of it to be found, supply will increase, reducing the value, so as investment strategies go, this is strictly short-term, but it can be extremely lucrative in that short-term. The longer the period of time that passes without such new sources being discovered, the greater the risk that the “incentive” will be removed.

    The second factor that should be contemplated under this topic is similar – if there is a suspicion or expectation that demand will shortly increase substantially, there is an immediate increase in the desire for the commodity. Wheat, if a drought is expected (and again if one is actually underway or worse than forecast), for example; steel, if war seems imminent; and so on.

    And of course, in third place, is the unsubstantiated but pervasive wild rumor.

    Put all these together to estimate an increase in demand using the Superstition Scale as a basis.

Commodity Value

Okay, so you’ve moved left and right and up and down on the table like a drunken sailor. The greater probability is that you’ll have moved down and right, if at all, unless a differential in scale has been necessary to keep your movements “within bounds” of the matrix. The result is that you have ended up with a number in a cell.

That number is the result of taking all those factors into account and applying a liberal degree of fudge factor.

It is the value, as stated earlier, of 1 [unit 2] of the commodity, relative to 1 [unit 1] of the basis. Actually, that value is x10 to the power of the result.

That sounds complicated, doesn’t it? It isn’t.

  • Write a 1.
  • Look at the whole number that is part or all of the answer. If it’s more than zero, write that many zeros after the 1.
  • If it’s less than zero, move a decimal point that many spaces to the left – which means writing one fewer zeros than the whole number.
  • Now look at the part after the decimal point, if any.
    • If it’s 0.25, write “1.778×” in front of whatever you’ve already written.
    • If it’s 0.5, write “3.1623×” in front of whatever you’ve already written.
    • If it’s 0.75, write “5.6234×” in front of whatever you’ve already written.
  • Perform any calculation to get the value of a commodity relative to the base commodity, in the units specified.

Hint: you are best of guesstimating the scale of the eventual value and using that as your basis. If you expect the price to be in Silvers, start with 1 silver. If you expect it to be in the tens of gold, start with a basis of 10 gold.

Image by Omar Hadad from Pixabay, cropped by Mike

An example

Let’s work a practical example: a rare wax created by giant bees that is especially efficacious at neutralizing poisons when a small quantity is added to boiling drink or food being cooked.

Base value: 1 gp.

Initial position: 1,1.

1. Initial Scarcity (relative to gold in this case): +5. The value 5 to the right of the starting position is 1.25.

    2. Danger Shift: +4. Giant Bees, individually, aren’t much more dangerous than many other creatures – though they could kill a serf or a child – but they don’t come individually, they come in swarms of 20 or more. And they can fly.
    The value that’s 4 to the right of the 1.25 is three across and one down (to stay within bounds), giving 2.25.

    3. Scaling Shift: To give myself a little room to move, I’m going to shift from 1 gp weight to one 100th of a gp weight – that’s an 8-space shift to the left, and brings me back to a value of 0.25.

4. Base Demand: This substance would have great portability, even more than gold, so I am going to shift the value two spaces down, from 0.25 to 0.75.

    5. Practicality Shift: This stuff isn’t a cure-all, or a total preventative. But there is still very definitely a practical purpose, and one that nothing else matches. That’s up to six steps down. However, a cheaper alternative does exist: food tasters. So that’s half the 6 steps = three. Three steps down from the 0.75 is 1.5.

    Of course, that’s assuming that the stuff really does what it is supposed to do. It might just be a superstition. But this is a fantasy game, and fantastic substances and cures and treatments are par for the course, so I’m going to say that the assumption is correct. So let’s talk superstitions.

    Image by Csaba Nagy from Pixabay, cropped by Mike

    I can easily accept that it might be believed that a dose of this stuff would ward off colds and chills and help prevent wounds from becoming infected – whether it really would or not. That would fit with the modern mind considering it a antibiotic, so players would also be prone to accept this; the GM might know better (it’s magical, not medical) or may not have made up his mind on the subject yet. That doesn’t matter; the belief alone needs to be taken into account when assessing the demand for the product. So, while it’s not a vitality potion or youth potion or anything like that, it’s still pretty good stuff if the superstitions are correct; I can’t see it having only a 2-space increase for this factor, nor can I see a 4-space increase as making sense. Right in the middle is a three-space increase, so that sounds good (and it also matches the impact on demand of the actual proven effect of the stuff). Three steps down from the 1.5 becomes 2 steps down and one right, giving a value of 2.25.

    6. Economic Shift: This stuff might be rare, but it’s also going to be fairly fragile. I can’t see it being robust enough to be a medium of exchange. But Gold is a currency – one of a set. So I now have to move three spaces UP the chart because the basis of comparison has demand factors that don’t impact the commodity. Three steps up from the 2.25 gives me a value of 1.5.

    7. Incentive Shift: I can believe that the nobility might put a bounty on this stuff in terms of tax relief. It’s too dangerous gathering it to try and make it a royal monopoly, so they have to accept that half of what it’s found will be expended by the superstitious, leaving only half for those with a reason for their paranoia. There is, however, no reason to expect that demand will suddenly increase, and there are no wild rumors circulating about it, so that’s the only source of an incentive shift, and it’s going to be mid-sized – two steps sounds about right. Two steps down from the 1.5 gives me an ultimate value of 2.

8. Commodity Value:

  • Write a 1.
  • Look at the whole number that is part or all of the answer. If it’s more than zero, write that many zeros after the 1. In this case, it’s a 2, so write two zeros: “100”.
  • If it’s less than zero – it’s not.
  • Now look at the part after the decimal point – there isn’t any.
  • Perform any calculation – there isn’t one.

Result: So, the end result is that 1 one-thousandth of a gp in weight of this stuff is worth 100 gp. That’s probably a single dose. This seems completely in line with magical potions, which might be guaranteed to work, but cost more.

But what if:

Example 2

I’m not going to work this example all the way through. I just want to give an example of the final step which has something after the decimal point:

8. Commodity Value:
Matrix result = 1.75

  • Write a “1”.
  • Look at the whole number that is part or all of the answer. If it’s more than zero, write that many zeros after the 1. In this case, it’s a 1, so I write one zero to get “10”.
  • If it’s less than zero – it’s not.
  • Now look at the part after the decimal point – in this case, .75.
    • If it’s 0.25 – it’s not.
    • If it’s 0.5 – it’s not.
    • If it’s 0.75 – it is – write “5.6234×” in front of whatever you’ve already written, giving “5.6234×10”.
  • Perform any calculation: “5.6234×10” gives 56.234. If the units were 1 gp and 1/10th of an ounce – about right for an exotic perfume, say – then a bottle with 1/10th oz of perfume in it would cost 56gp, Two ounces worth would be 112gp, and so on.

But what if:

Example 3

A third example again restricted to the final step, to demonstrate working with a matrix result less than zero:

8. Commodity Value:
Matrix result = -1.5. This can happen when there’s a scale shift that doesn’t go far enough.

  • Write a 1.
  • Look at the whole number that is part or all of the answer. If it’s more than zero – it’s not.
  • If it’s less than zero – it is, it’s minus-one – move a decimal point that many spaces to the left plus one – which means writing one fewer zeros than the whole number. So I have to write 0+1=1 zero and then a decimal point in front of them: “.01”
  • Now look at the part after the decimal point – 0.5 in this case.
    • If it’s 0.25 – it’s not.
    • If it’s 0.5, write “3.1623×” in front of whatever you’ve already written. So I get “3.1623×.01”.
    • If it’s 0.75 – it’s not..
  • Perform any calculation: “3.1623×.01” gives 0.031623 as the result.

Obviously, this is not a very useful result – it might be 1 pound of this stuff having a value of 0.031623 gp. There are two things to do: change the scale, and change the currency for something smaller.

Stones are a unit of measurement rarely used except when it comes to human weights, these days. A better choice would be to say that 100lb of this stuff costs 3.1623 gp – which can then be translated into gold, silver and copper according to the values in whatever game rules you are using. So this is sold like bags of concrete.

Exponential math

This system works by virtue of the mathematics of exponentials – I’ve done it all by base ten, so ordinary Logs and ten-to-the-x give simple results.

10^n × 10^m = 10^(n+m).
10^n ÷ 10^m = 10^(n-m).

But the system hides most of this complexity from the user.

So, if you have a × b × c ÷ d, you can work it by getting the log of each item (a, b, c, d) and calculating e = log(a) + log(b) + log(c) – log(d) and then working out 10^e.

That’s exactly what the system does – with all the mechanics under the surface.

Just thought people might want to know.

Practical Usage

Look, most of the time you won’t need to use this system – you can simply pluck a value that seems reasonable out of thin air using established prices as a guideline and a precedent. If you have to, you can use the values given here as a basis for adjusting those values – if something, say “Moonwood,” suddenly becomes more dangerous to gather, the single factor is all you have to change, and the rest works itself out. You can apply this system in part, not just in whole.

It’s a resource – use it to expand your repertoire and put some structure into your price-list.

This isn’t the first time I’ve written about valuables and how much coins might be worth. Those looking for more might find the following to be useful:


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