What's your local minimum wage?
What's your local price for butter, eggs, flour, sugar?
WE cannot possibly give you a price quote because we have no idea of what YOU will have to pay for ingredients, or what you should be paid for your work.
YOU have to figure those things. Now because you have already been baking, you know how much your cake costs and how long it takes you to make. So decide how much you want to be paid per hour, and do your calculations accordingly.
Please--this isn't any different than scaling a recipe to double or half. If you can bake a cake, then you can do the arithmetic to set a fair price.