AHow big are the cakes? How much do you think you would need to spend on ingredients, and how many hours will it take to complete the order?
BTW you would need permission from the copyright owner of the Playboy logo before you would be able to legally recreate it on a cake for sale.
Do you want to cater to people who only want to pay pennies OR are you going to charge what the *work* is worth? Jason is right on both counts - figure out what your costs are to make it and no, it cannot be legally sold w/o permission from Playboy.