I'd say nothing.
As long as musicians have to make a living, they have to charge money for their music. Unless they can handle all the business of distribution themselves, they need to have someone else create web sites, CD's, downloads or whatever. That means the middle men must also charge money for their services.
Competition helps keep prices down, but it also means that people are competing for consumer's attention, and that means marketing, and that means glitz and pizazz, with a capital G, and a capital P, and that stands for Pool!
Much marketing is honest and often low-key, but there will always be the hucksters, both promoters and musicians.