When a Dollar is not a Dollar

I gave my 5 year old son a dollar to spend at the canteen. He got really annoyed and said that it was not enough and started to cry. I tried to reason with him about how a dollar was plenty. He wanted to go and raid his piggy bank for more. Clever Mummy worked out that it was not the amount, but the number of coins that was the issue. He was very happy to accept 5 twenty cent coins instead. More traumas later when he complained that the canteen was keeping his money when he bought things. Introduction to the Capitalist Economy 101, from Dad later, he was still not entirely thrilled. It just seemed soooo unfair for them to take his money.