Clear Channel have some insurance against losing their domination of the music biz: they own the major booking company SFX (was PACE) and have exclusive city contracts to many of the nation's medium to larger venues. Down here they even own a few of the smaller clubs.
I haven't investigated it much but I believe that Prince's group does not use SFX. They seem to barnstorm into town with a few weeks notice, booking the Summit/Compaq Center (where the Rockets play). He walked away from WB years ago and sells his CDs at his shows and online (I don't know if he even places CDs in stores anymore although he did market one set through Best Buy).
A couple things not mentioned in this article are "studio time" and "advertising". Prince owns his studio and isn't doing much advertising.
The Cramps went self-published this year too. They would produce their own albums and give them to the label ready to release. They never felt that they got a fair shake and heard that some bands signed to labels because they figured if the Cramps were there, then things must be okay. The band owned clear title to most of their work (not their I.R.S. recordings apparently) and have rereleased them on remastered vinyl and CDs.
A band can get rich without chart success or radio airplay (Iron Maiden built up a sizeable following with continual touring but with Clear Channel's lock on the concert biz tied with their lock on radio, I don't know if a new act could find such success).
The good thing is that an artist doesn't have to sell as many units to get the same kind of money as on the major labels but they probably won't have anywhere near the same kind of fame. Since chart position comes from "soundscan" sales reports, most album sales by indie artists won't be tracked. Big Label will continue to "toot" their own successes with Grammy Awards, RIAA Gold Records, etc.