People in the Grendel market simulation have needs. There are three tiers, corresponding to necessities, nice to haves, and luxuries.
How much are people willing to pay for a necessity? Create a budget (half of current cash, for example), and divide it by the total number of necessities. So if you have $100, and your necessities are six bread and four fruit, you’re willing to spend $10 per item.
But your necessities aren’t really six bread and four fruit. A better approximation is “ten of something food-like.” So if bread is selling for $12 per item, and fruit for $8, you’ll spend your budget on, for example, seven fruit and three bread, paying $102 and being slightly less happy than six bread and four fruit would make you.
Bread isn’t really selling for $12 though — that’s just what the baker told you. You could offer $10 and see what happens. Maybe he’ll accept that, or maybe he’ll make a counter-offer of $11. That might be okay.
If you wait until the end of the day, the bread might be cheaper. The fruit too, but maybe the discount is less because the fruit isn’t about to go stale. If you were buying fish, you’d probably get a really good price at the end of the day.
But if there’s not enough bread to go around, you can’t wait, because there won’t be any left to buy. People can spend energy to get to the front of the queue.
These are some of the things Grendel goes through to make the markets work. I’ll quantify it in a later post.