I'm confused about something. If I make cupcakes out of a cake mix, it makes 24 cupcakes, thus 24 servings. When I use the doctored recipe, it makes 36 cupcakes, thus 36 servings. Using the same amount of batter, I make three 8" layers, making one 8" cake, about 6 inches high. But if the round cake is cut into wedges, I can't get more than about 16 slices. Is a serving of a round cake bigger than a square or a cupcake? How do I make that same amount of batter equal 36 servings?

Industry standard for a serving size is 1x2x4 OR 2x2x2....both yield the same amount of cake
Figure your serving yields on how much batter you use....one cake mix will make one: 10x2R; OR 8x2 sq; OR 12x8x2; OR most any of Wilton's shaped pans.
OR one 8x2R + 6x2R; OR a few others I can't remember right now.
Most of us tell customers those sizes will serve 15-20 and base our pricing on that. Yes, you do get 24 cupcakes but it's hard to cut into sqs or slices and get the same exact #

First, you're thinking too hard!

A slice of a 3" cake is a lot more cake than a cupcake.

so does a round cake get cut differently to make more servings that aren't as huge?

Yes it does. Indydebi shows how to cut a round cake on her web site. I believe it's www.cateritsimple.com but I'm not sure.

Here's the actual page on how to cut a cake: http://cateritsimple.com/_wsn/page19.html

As stated above, an industry standard serving size is 1x2x4, which is 2 layers, cut in a 1x2x4 rectangle ... it's been said this is about the size of a folded peanut butter sandwich (see pics of cut cake pieces in the above link.

So if you have a 3-layer cake, the customer is getting 50% more cake, so the price should reflect 50% more. i.e. if an 8" cake make 24 of the 1x2x4 pieces, and assume your rate is just $2/serving, this 8" cake would sell for $48. BUT ...... ! If it's a 3-layer cake, they are getting 50% more cake EVEN THO' THEY CAN STILL ONLY CUT IT IN 24 PIECES!! So they would pay $48 + $24 (50% more) = $72 for a 3-layer, 8" round cake.

Cake is charged per serving .... that's per serving that the cake is DESIGNED to serve, not the number of pieces they plan to cut from it. So as you are setting your pricing rates, you need to pick a chart (any chart) and stick to it for pricing purposes.

you do not have to go into the calculations with the customer .. they just want to know the price. "2-layer 8" cake is $48 ... 3-layer 8" cake is $72. It will serve 15-24, depending on how you cut it."

Thanks, indydebi! I knew there were more servings, but now I see how to price it by servings, instead of by slices. And slicing it your way will definitely yield more servings.