Britney never paid a due ever. Her people are selling a cute smile and a killer body. ANYone can sell that. Music is NOT a part of the equation. Kids buy anything new and pretty ..... much like beer drinkers.
As for selling art - that's a tough order. There is no way to fairly price the value of art because it is not worth the same to everyone. As an artist, you must FIRST be satisfied with the creation of your work. If it sells, then that's a bonus, but the true joy comes from the creation itself. Performing arts are a rare and unique gift that need to be shared, but they are not always a source of financial gain.
In order to market a successful career in music - your own needs and wants are SECOND to the needs and wants of the client. maybe you were playing for yourself?
(not a bad thing ...... just maybe not what people in that shop are willing to listen to)
Don't give up ....... search your soul to find the center of your desire, and then see if it can fit into the harsh, cruel world of the entertainment industry. Even at the coffee house level - it's still show BUSINESS, not Show "art". It's a beautiful thing when art is appreciated, but it's MORE important that someone actually CREATE the beauty. What people buy, will change so fast - your head will spin, but the creation of beauty will last forever.
Good luck, my friend .... it gets easier with time.
Every instrument, every voice, every sound in nature ... these are are all my private tutors ... 24/7 for free, and all I have to do is listen.