One day last year, an engineer and I went to a pizza place for lunch. The engineer told me he wasn't very hungry, but he said he was going to get the 12-inch medium instead of the 8-inch small — because the medium was more than twice as big as the small, and it cost only a little bit more. This sort of blew my mind. So I went big on the pizza-value question. The graph below is based on 74,476 pric