Back to the pizza thing for a second...
A couple of months ago I ordered a medium pizza and when I went to pick it up the girl at the register said "We were out of mediums so we are giving you a large for the same price" I was really happy!
Three days later I ordered a large pizzafrom the same place. When I went to pick it up the same girl was at the register.
I said "I was in here a couple days ago and paid for a medium pizza but you gave me a large pizza for the price of a medium because you were out of mediums. To make things fair I ordered a large pizza today and I want to pay for a medium pizza instead just to even things out."
The girl said thet she remembered me and that I was nice for wanting to make things fair.
So she rang me up for a medium and gave me the large pizza and I left!