What's the currency of your world? Dollars? Pesos?
Or maybe they trade with other goods?
Or did you make up a currency name?
Do you know how much a potato is in your world vs in the country that you, the author, lives? Which is cheaper? Now that, is an interesting question, huh? ;)
I heard J.K. Rowling has a very specific currency system for her wizarding world :O
I'm sorry, but I can't do the math XD I'll leave that to the experts.