With Dominos pizza, I already have the feeling my toppings are random. That is, sometimes I get a lot of topping, and most of the time but not always I get very little topping.
I think all the major chains have a policy in place where you get the exact same amount of toppings by weight no matter what you order. If you only order pepperoni you get a ton of pepperoni, but if you order supreme you get less of everything but it ends up being the same overall by weight.