Today perhaps. But in the past the artists money from selling records. So the tour was to promote the album, rather than the other way around
At the high end, live performance pays more than it ever has, since the exclusivity is what people are paying for. At the low end, the performers get squeezed because they are competing with lots of amateur DJs or people simply doing without a human.
They have to dedicate a decade or more of their life at a prime age to the character - selling their soul if you will. And not going nuts in the process. Fame and extreme fame would turn any normal person crazy. But you don't have the option of withdrawing, because you have this army of other people depending on you, among other things.
100%, I do feel like fame at such level is a very net negative thing to have. You do get money and fame and there are many times within the media where paparazzi and others have made some celebrities lose their mind. And almost everyone loses a sense of something human with this sense of fame. From Princess Diana to Britney Spears to Justin Beiber.
The tragic true story of Justin Beiber: https://www.youtube.com/watch?v=RvnnbzcAjOU
Music labels contracts have always been exploitative, they usually require the band to pay back costs like studio time, producer, mix/master engineers, marketing, before getting their cut of royalties in sales, for artists without clout the royalties share would be 75/25 to the label (or worse), more famous acts can get a 50/50 split, again after recouping the costs.
As any passion industry it is extremely exploitative, as much as people like to hate on streaming platforms nowadays the music labels have been the most evil aspect of it all for 70+ years and they managed to lurk in the shadows without attracting a lot of flak.
Authors would get something similar, they'd rarely sell out their advance, but could buy copies for pennies on the dollar and sell them at conventions.