My children's first economics lesson

A couple of weeks ago, I was driving around with my two 4 1/2 year old twins, and we drove by an ice cream place that we used to go to sometimes, and my daughter asked, "Why don't we go that ice cream place anymore?"

I explained to them that I thought the prices were too high for what you get. They didn't quite get it, so I said, "Imagine there are two ice cream stores right next to each other, and both stores served the same exact ice cream. However, one store charged $10 for a cup of ice cream, and the other store charged $3 for a cup of ice cream. Which place would you go to?"

First they said that they would go to the store that charged $10. After all, $10 ice cream sounded better than $3 ice cream. But I reminded them that the ice cream in each store was exactly the same, and asked, "Why would you pay $10 when you can get the same thing for $3?" And finally, the light went off.

I asked, would anyone go to the store that charged $10? And they said "no".

Pushing the issue, I then asked, should the ice cream store that was charging $10 be able to force the other ice cream store to also charge $10, so that it's more "fair". And they said "no". First lesson complete.