She’ll probably make more money than she would going through Amazon, let’s say, but not a ton more. Do you imagine she’d actually swallow Amazon’s standard deal to put her books on their site? Of course not.
Superduperstars are always going to run their own show. Floyd doesn’t need a promoter any more than Jaden Smith needed to bust his ass at auditions.
Note that Floyd hasn’t signed any other decent fighters, Jaden hasn’t written a book divulging the secrets of succeeding in showbiz and Rowling won’t distribute any books of note other than her own.
The tables get turned all the time, relax. Incumbent specialists have nothing to fear.