Geometry Saved Me Money, from Binary Dollar, via Grey Matters. Which is more: a twelve-inch pizza or two eight-inch pizzas?
The twelve-inch pizza, of course; it is more square inches of pizza. (I'm assuming all pizzas are equally thick.)
However, if you really like crust, the two eight-inch pizzas might actually be the better deal. One twelve-inch pizza contains 36π square inches of interior and 12π inches of crust; two eight-inch pizzas contain 32π square inches of interior and 16π inches of crust. So if you're willing to trade 4π square inches of interior for 4π inches of crust, take the smaller pizzas. That is, if you'd rather have a third of the crust of the pizza than a ninth of the interior, or if you'd prefer three crusts to one crustless slice.
I like the crust, so I might.
(This analysis assumes, of course, that the thickness of the crust is negligible, so that "an inch of crust" actually means something.)
The waitress in the restaurant where this question came up thought the customers would prefer the two eight-inch pizzas because it was more "slices of pizza". Maybe it's just me, but a "slice of pizza" is a meaningless unit, because it's not standard. I would have at least expected the argument that eight plus eight is more than twelve.
I suspect that pizza is the food that is most often "illogically" priced. I've seen, say, chicken wings sold at "10 for $5, 15 for $8" but you don't see that too often, because most people can do the math and realize that buying 15 is a bad deal. (Think of it this way: what if I want thirty? I can get three 10-packs for $15, or two 15-packs for $16.) But with pizza people will throw up their hands. Also, I have seen places where a larger size of pizza costs more per square inch than a smaller pizza (I can't find any right now); I was once told that this was because for whatever reason the large size was more inconvenient to make (it fit in the oven funny, for example). That at least seems like a plausible economic reason; it's clearly not the cost of the ingredients and almost certainly not the labor.