To me, it is about the numbers. Add up your total food costs, and your sales. If the numbers run right, then throwing out pizza seems irrelevant . . . a cost of doing business as a buffet. If your overall food costs run 30% or lower, then game on.
Seems that if your numbers are off, you can choose to dump to buffet or raise your prices to make your margins. I suggest that the key is to set a measurable goal for lunch and assess if you are meeting it. If you are not, then change the steps you are taking. It could be gross revenues or profit margins, or food costs margins, or whatever. Get something measureable so you aren’t 'gut feeling" it and getting caught in details that could be meaningless.
I am betting CiCi’s adds in a margin of waste into their pricing structure. Maybe you should as well.