they probably insured this. Or just put the amount of pizzas made into their advertising dollars. Instead of doing a during the game ad costing 3.5 mil to 6 mil they did this deal.
The labor is essentially already paid for to make that extra pizza. It only really costs the raw ingredients which probably cost less then a dollar a pizza.
Add the free advertising they get from this (see this thread) they are hoping this is plus ev for them.