How does pricing work if you have a request for a cake (fondant) that serves about 100 people, but they want sheet cakes (buttercream) to feed another 100 people? Do you price out the actual cake per serving and the sheet cakes per serving to get a total. Or, do you just go off of the total servings?
some people have another price from 4" tall cake to 2" tall cake (or a kitchen cake 4" tall, but this is undecorated) Personally i charge the same per serving no matter what shape/height/size it is (unless carving gets involved) . I don't care what the event is, what the shape is, or who is cutting it. I use 8 cubic inches (1x2x4 or 2x2x2) as a serving slice and charge the same price per serving.
Do you have a seperate price for your fondant cakes? If so, that in my opinion should be the only difference in the pricing.
If they want to order the sheet cakes to cut costs, personally I'd point out ot them, other than the fondant costs, it will be the same.
I also wouldn't want to be at that party where part of the people get a 4in layer slice with filling and the other half get a 2in layer with nothing but icing.