There is nothing wrong with imagining a world where 50,000 gold pieces is a reasonable amount of money to buy a sword.
But in this opinionated rule set, money is reexamined in an attempt to find a reasonable compromise between the reality of historical currency and metal values, and the need for a fantasy in which adventurers could even find a market to exchange coins for useful items in the first place--something that the medieval world of history would have not likely been able to offer.
First things first:
Metals and Coinage
Gold is an exceedingly rare metal on Earth. As of 2021 CE, all of the gold ever mined on Earth in history could fill 3.4 Olympic-size swimming pools. While that is a lot of coins, if one subtracts all of the gold used to create anything that isn't coins, it doesn't leave much to circulate throughout the world.
Gold coins have also not historically seen much use--they had a brief period of popularity in the decidedly post-medieval Age of Exploration, as a way to cart tons of purloined gold from the New World back to Europe, for example. But if you're looking for a currency that ordinary (upper middle class) adventurers would use to buy goods in town, gold is just a non-starter. In the U.S. in 2021, most points of sale won't accept $100 or often even $50 bills, so it's difficult to imagine an everyday currency valued at $1,000 or more being of much use.
Silver has enjoyed some use as a currency. The GBP was originally based on a pound of sterling silver, and was divided into 20 shillings. In medieval times, a shilling was comparable to the value of a single healthy sheep...an amount a commoner would understand, though still far too expensive to throw down for a few drinks at a tavern. The shilling was further subdivided into 12 pennies, which were, in those times, further subdivided into 4 farthings. A commoner could be expected to deal in pennies and farthings...if they had much use for coin, which most didn't.
But then, adventurers aren't buying magic swords from serfs. They are shopping in high-end mercantile districts in cities, where smiths, expecting some demand from adventurers, have crafted fine weapons, armor, and other trinkets, hoping to sell at a premium. A few pounds sterling isn't a crazy asking price for a suit of metal armor--and the sky's the limit of you're making something fancy for a lord or king.
Of course, a pound of sterling would make a hefty coin, and so a gold coin could step in as a more portable alternative, for those needing to conduct business in multiples of a pound.
Nowadays, nobody likes systems of division by 12, 20, etc. We don't need to stray too far from historical precedent to find a nice base-10 system that will work well for adventurers in a pseudo-medieval world.
Oh, and, as for the other metals:
- Copper currency is practically unknown in medieval history, but fantasy fans love it, so we'll let it slide.
- Platinum was essentially unknown until centuries after the end of the medieval period. It has no place in this system. It's also barely more valuable than gold--certainly not 10 times more so. If we need something fanciful that outvalues gold, why not make something up? This is a fantasy world after all.
Standard Coinage in Medieval-esque Worlds
| Coin | Abbreviation | USD 2021 | Metal Content | Weight | Diameter | Thickness | Nearest historical equivalent |
|---|---|---|---|---|---|---|---|
| Gold Crown | GC/GP | $1,000 | Gold | 3.5g (0.12oz) | 20mm (0.79in) | 1.85mm (0.073in) | Librus, pound sterling |
| Silver Shilling | SS/SP | $100 | Silver | 8.6g (0.3oz) | 30mm (1.18in) | 2.00mm (0.079in) | Sesterce, shilling |
| Copper Penny | CP | $10 | Copper, tin | 2.5g (0.09oz) | 17.5mm (0.69in) | 1.52mm (0.06in) | Penny, denarius |
For reference, coins in circulation in the U.S. in 2021:
| Coin | Weight | Diameter | Thickness |
|---|---|---|---|
| Dollar | 8.1g | 26.49mm | 2.00mm |
| Half Dollar | 11.34g | 30.61mm | 2.15mm |
| Quarter | 5.67g | 24.26mm | 1.75mm |
| Dime | 2.268g | 17.91mm | 1.35mm |
| Nickel | 5.0g | 21.21mm | 1.95mm |
| Penny | 2.5g | 19.05mm | 1.52mm |
What can you buy with a few:
- Gold crowns: a horse, plate mail
- Silver shillings: a sword, a complete middle class outfit, a set of professional tools
- Copper pennies: a fine meal, a night's stay in an inn, a night of drinks, a shirt or trousers
Conversion to other editions
Generally, speaking, the conversion rate for 3e goes through the USD equivalent. That is:
- 1 Gold Crown = $1,000 USD 2021
- $1 USD = 1 3e GP
- +5 sword in 3e = 50,000 GP = $50,000 USD = 50 gold crowns
This is useful as a guideline for 3e conversion.
For 5e, it is useless. 5e magic items have no useful price equivalency. Since money cannot buy items, it is functionally useless for adventurers; 5e essentially has no economy at all.
The proposed solution: completely replace the magic item system.