re: Charging per serving: which serving size do I use???

The 30 servings I calculated was using a wedding cake serving guide. She wants the two tiers of 8" and 6" even though she is only serving 15 people. I don’t want to end up having two prices for the same size cake… Such as a price for party servings and a price for wedding servings. I think I may try a different pricing approach and charge set price for each size, charge a price to tier them, and a price for add on decorations. Pricing them is harder than making them!!!