So our headcount ended up being far less than expected. When we signed with our baker we estimated 120 guests for her. Well, our final number is 87. We are doing a small 2- tier cake for cutting and then the rest cupcakes. When she saw our smaller number she suggested instead of doing 2 tiers of cake, doing 1 tier with a "dummy" styrofoam tier on top. Since her cake is a little more expensive than cupcakes (50 cents) per serving I thought this was a good idea. Well, today she sent me the final invoice, and on there was an additional $20 for an "artistic fee" for decorating the dummy tier, which she didn't mention when she suggested it. It seems reasonable, but it changes the math on it.
She's been a super helpful vendor and I don't think of her as someone trying to pull one over on us. But, with a real instead of dummy tier we would have an extra 10 servings of cake and 10 less cupcakes...which is a difference of only $5. But this adds on $20 so actually by doing the dummy tier, the total is $15 more. I don't want to be super cheap or ungrateful to her since she's ending up with less money than expected (but hey, it is an estimate, these things happen), but for the exact same amount of cake, why pay $15 more?
How should I mention it to her without sounding like a pain?