Our Daily Bleg: What Economic Concepts Should Kids Know?

(Hemera)

This bleg comes from reader Wayne Smith, who asks for suggestions on which economic concepts are the most important for kids to learn:

What topics do the Freakonomics readers feel are most important to teach kids 8-13 years old? Aside, of course, from the fact that the man keeps you down.
I was listening to The History of Sesame Street audio book the other day and thought that it would be nice to come up with a YouTube show with decent production value that outlines basic economic concepts in an entertaining way. Concepts like capital, value, supply/demand, trade, time value of money, interest, saving and borrowing, opportunity cost, taxation,and so on.  This would be more narrative than something like Khan Academy.  Naturally each concept can have an episode devoted to it and each concept can be addressed in different ways in different episodes, but in scenarios geared toward kids.  What do the readers think about this as a concept?