good job Jonathan, unfortunately, there are some people like that who feel they don't need to pay for a service. Hope you can find them and humble them. Baking is not an easy job, period. My dad is a trained chef and he's afraid of baking because of the specific measurements and special steps in order to accomplish a delicious outcome. Also, its arduous work.
If they received the cake, they need to pay for it. And if they don’t like the taste, their fault for choosing it. They have taste testing for wedding cakes.