One: Incentives matter. Two: There’s no such thing as a free lunch.
I don't think I like this game. Without disagreeing about the importance of incentives and opportunity costs, I would say that economic growth matters a lot, and that people should know how much higher our standard of living is today than it was two hundred years ago. And they should realize how much of the increase is due to the accumulation and application of knowledge.
Furthermore, people should know that international trade is a positive-sum game. And that markets alleviate shortages, while price controls cause them. And...
For Discussion. How many things belong on the list of "two (or more) things" that everyone should know about economics?