The brides go for the lowest price because they don’t know any better. They’ve never hired a musician in their life and probably won’t again. So maybe the answer is to do a “dog and pony show” where you explain to the bride all of the things that you mention in your post, without making negative remarks about anyone else. Just say that these are the things that can make or break the ceremony and not all harpists can do this. It’s like making a musical soundtrack for a movie. It has to compliment the movie without taking over or messing it up. If you can establish a feeling of confidence then maybe the commitment rate will go up.