It does not matter if you are writing medieval or modern stories, you are going to need some sort of exchange system. If your character wants something from a man, and that man wants something of equal value in return, what does your character get? Is it currency? Or is it a trade (for example, tomatoes for potatoes)?
If it is currency, the first thing you will need to do is come up with a material for the currency to be made out of; such as coins, paper, or jewels.
Today, we use paper for bills, and because of that, we have had to come up with security measures to stop others from making it themselves. We have holograms, hidden ink, raised text, and more and it’s all because our currency is made out of readily available material.
This problem is why so many novels use precious metals like silver, gold, and copper. If someone were to find a hunk of gold, well it is easy to say that the hunk of gold would be worth equal to the weight of gold coins.
Creating a money system for a world can seem overwhelming, but it does not have to be. Technically, all you need is one coin. For example, in America you can buy anything with enough pennies; anything at all. You want a car? You can do it with enough pennies. It is the lowest increment of money they have, and technically all you need. The only reason why we have coins of higher value is that it is a lot easier to have a dollar than it is to carry around a hundred pennies. So, once you come up with the lowest increment coin, anything else you add is just for convenience.
With money material and increments done, now comes the final step. Make a list of items the average peasant would need(such as bread, clothes, milk), and price them at the lowest value one could buy them for. This will be your base on what things will be worth in your world.
Using the bread as an example, if you say that the absolute lowest price you can buy bread for is 10 gold, then if someone buys bread for 40 gold, you will know that the bread they bought was far higher quality bread than what a poor peasant would buy.
Here are some steps to follow:
- Figure out what your currency will be made of.
- Figure out what currency increments there are (penny, nickel, dollar…)
- Make a list of basic items, and price them at the absolute lowest price they could be purchased for.
- Come up with some currency designs (like a gold piece having the king’s head on it)
- Come up with currency names. For example, 1 cent is called a penny. Does your money have nicknames?