Here's a proof for the crust-to-toppings ratio, btw. (With the big assumption that crust thickness is equal for all sizes of pizza, which might not be the case!) Let Ac is the area of the crust. Let tc be the thickness of the crust.
Ac = pi(r2) - pi[(r-tc)2]
Ac = pi[r2 - (r2 - 2r*tc + tc2)]
Ac = pi(2r*tc - tc2)
So let's look at a 6", 8", and 10" pizza. A 6" plus an 8" equals one 10" in area. Let's assume the thickness of the crust is 1 inch.
Ac6 = pi(2*3*1 - 1) = 5pi
Ac8 = pi(2*4*1 - 1) = 7pi
Ac10 = pi(2*5*1 - 1) = 9pi
Ac6 + Ac8 = 12pi > 9pi = Ac10
So, because everything in pi(2r*tc - tc2) is a constant except for r, it only depends on r. And the only way for 2 pizzas of the same area to have the same amount of crust as the larger pizza, they must have an average radius of (r + tc)/2. And that is not possible for any feasible value of tc. The optimal distribution of two smaller pizzas would be two pizzas with radius=r/sqrt(2), and the only crust thickness at which two smaller pizzas' crusts equal one larger pizzas is with tc = r(sqrt(2)-1), which would be at the point where the crust's thickness would be more than 40% of the pizza's, at which point you return the pizza to the store because that is ludicrous.
Someone please feel free to check my math. I feel like I made a mistake somewhere.