can anyone tell me what size tiers i need to serve 50-60 people, three round tiers, but am planning to carve down the sides(which i've never done before). not sure how to estimate this. was thinking i'd carve down 2 inches from top to bottom. if i carve less than that will i still get that whimsical effect? thank you

Do you mean just rounding the top edge? That's what a beveled cake is.
If you mean tapering from 9" on top to say a 6" on the bottom that's different.
For pricing you charge as if all was a 9"er.
For servings I'd guess similar. You want a total of 60 servings from 3 round cakes then I'd suggest using 10x4" rounds - they can be tapered down to 8" on the bottom and still have enough cake.

beveled cakes use beveled pans. It doesn't affect the servings at all.

I think you're doing a carved cake so the above advice is spot on.

i was using the wrong term--i plan to carve the cake down so it is bigger on top than on the bottom. so my question is, if i want three carved tiers, what sizes do they have to be to have enough servings. 12, 9, 6 or 12,10,8? to get the whimsical effect would i carve a 12 inch down to 11 or 10 at the bottom? sorry for the confusion