Change?

Yesterday our next-door-neighbors had a yard sale.  Luke picked out a few items and was able to calculate that he would owe $2.50 total.  When I handed him three dollar bills with which to pay, I realized that he didn’t have any concept of getting change back (in a world where most of our purchases are done with plastic).  Our neighbor was very kind in talking him through how much he owed, how much he was paying and how much he should get in change.  When we got home, I was attempting to explain the concept of change and why it is that you might over-pay for an item.

Mama: Well, sometimes if you don’t have the exact amount you owe, you have to pay more than you owe.  If you pay less than what you owe, you won’t have paid enough.  So you pay too much, and then they give you back the amount that was extra.

Daddy: Except when you buy Apple products.  Then you pay too much but they don’t give you back anything.

(Luke, with a puzzled expression on his face, looks back and forth between Mama and Daddy while they laugh.)