Let's say you want to go buy a loaf of bread. How do you pay for it with knowledge of energy sources? I'm quite sure the cashier would be quite tired after perf

Let's say you want to go buy a loaf of bread. How do you pay for it with knowledge of energy sources? I'm quite sure the cashier would be quite tired after performing the 300th viva of the day. Some people do trade knowledge of energy sources for stuff, using money as an intermediate store of value, but most people cannot, and it wouldn't be desirable either otherwise we wouldn't have a varied and healthy economy.