Hi sarahhelen, I recently read a super interesting article written by Carina's Cupcakes on Facebook. I think it could help you price your cakes a lot better:
We can't tell you how much to charge in absolute numbers because it depends on your location. So, to correctly price your cake you would have to charge for your work, in addition to charging for ingredients. The rate you can charge for your work depends on your level of expertise (I wouldn't call it professionalism). Your expertise is built on the experience you have making cakes, the number of cakes you already have made, the money you've spent on training etc. etc. So the higher you are trained, the higher the hourly rate you can charge for your cakes.
I would try to find a number that is suitable for your region as well. So in Spain, you should choose an hourly rate that other professionals charge. Are there any other cake decorators in the area? How much do they charge?
Many decorators don't charge enough for the hard work they put into their cakes. Granted, if you are at the beginning you work more slowly, you can't make the customer pay for all those hours. But you can definitely charge all the hours it would take a more experienced decorator to make the cake.
I think that Suzanne was trying to say: The more professional your cake looks, as in being served on a correct board, maybe even with a cake stands, and the more professional your working environment is (as in having a professional kitchen, paying all the taxes, insurance etc.) - the more you can charge.