And neither did I. But even in our simple market there could be a basic "imbalance" that is the result of the natural order of things.
If you have a child one day, you're going to need more than one loaf of bread from me every week. And you're going to need more than one head of lettuce, too. That means you can either figure out a way to get the extra food you need, or accuse me of "greed" and "profiteering" when I demand an extra head of lettuce every week for the extra loaf of bread you need from me.
How would you go about getting the extra food (both the bread and the lettuce) that you need? To make this really challenging, add this consideration: Growing two heads of lettuce a week already requires you to operate at 100% efficiency for growing lettuce, so it's not quite as simple as "growing more" on your own.