Two things. If you really care about the price difference between a med and small, then you may also be in a category that would be willing to eat the same thing again. I.e. You may not have a choice. At any rate it keeps for a day or two in the fridge, so it's not like you have to have it for back to back meals.
I'm failing to see the problem you see. If you don't like pizza why did you get it in the first place?
Its ok, one a week or whatever. Not some great delicacy, Especially not cold and day-old.
You know you can make things warm again with a microwave oven, right? ;)
Seriously though, there are people who will gladly eat pizza every day. Just because you don't like it (or maybe you just don't have any quality pizza restaurants nearby), doesn't mean it's a bad idea.