It is often very easy to look at a modern thing and assume that they reflect what stuff should cost in a fantasy game, but that’s not even close to the truth. I want to be able to say - A banana costs 50¢, and an apple costs 25¢, so if an apple costs 1cc then a banana costs 2cc in game. Yeah - doesn’t work. Here’s why.
Start with the cost of marketing in the modern age. How much does marketing cost? Compare the cost of a store brand cola to Coke (not on sale). Yeah - not only is the difference caused by the advertising, but Coke should be able to have economies of scale that allow it to be produced more cheaply.
Then factor in the automation. We go to the store and buy T-shirts for next to nothing. Fantasy era characters have to pay for the weavers and the tailors. These weren’t garment district illegals here, but skilled craftsmen. Don’t think about what it would cost for a shirt from Wal-Mart, think about a hand knitted sweater imported from Ireland.
Don’t forget that we get our fruit from South America, and it’s still cheap. The characters will only be able to buy those things that are grown locally IF they are in season. Fruit probably cannot be imported, because it would rot on the ox drawn wagon. There would be pickled versions or other preservation strategies, but fresh fruit from somewhere else? Forget it.
Grain Into Gold tries to show these issues and more in the pricing schemes. One of the major pluses that we didn’t mention here (but is in the book) is that there are fewer middle men. Think about how many shippers and forwarders touch the stuff you buy as it makes its way from China to the US. There should be far fewer of these guys in the way, making things that much cheaper. Just like real life, corn is a lot cheaper from the farmer’s road side stand than from a grocery store.