For dummy cakes done in fondant? 8,10,12 sizes?

Same as you would if they were real cake!

Sorry I couldn't be more help than that. I assume you were looking for an actual figure.

It's really the same amunt of work. The styro dummies will cost about the same as cake. Since you don't have to torte or fill, you could take 10% off your regular price.

I agree with the above post, pretty much the same as if it were a real cake. Most of the money is in the time it takes to decorate. But if you have to buy the dummies, then they still cost about the same as a cake (unless you KNOW you will be able to reuse them again quite often then you could subtract for this cost... but I would make sure you have your cost covered)