Ah, if only it were that easy!

Part of the problem is that there are 32 different toppings available which could be added to any pizza, but each pizza starts with a different set of toppings (about 4 or 5).

And that still doesn't get around the calculation problem of only changing the price when the extra toppings > removed toppings when above the basic price.

But thanks for the suggestion - there may be a direction to go in here.