Nobody buys their favorite music video (unless it's The Wall). They buy the CD, because all they really care about is the music.
http://www.amazon.co.uk/Various-Artists-Warp-Vision-Videos/d...
Thousand Foot Krutch made this project which was easily funded it seems. Although they are an established band already, and I'm not sure if 100k is "good" for them or not. But then again, that's only really pre-orders.
They made enough money to retire off their first album. Under the kickstarter model, they wouldn't have been able to earn anywhere near that much money as no one had heard of them outside of Seattle before their first album release.
Was making enough to retire their goal? Making enough to keep making music as much as they can seems like enough for a lot of musicians. If it could reach that level, I think it would be a "success".
The artist will only release if a certain threshold is reached.. Then the released music is completely "free" to share as people please. The artist is compensated as they see fit - they set the price in the first place, and also can use it to justify part of the price (to compensate for recording, hosting etc.).
"Piracy" then serves to generate rep to prove that they can deliver on future releases, there can still be people who make money in the middle - generating PR for the project etc.
The platform could take a small share of the cost, a slightly larger share for hosting, slightly more for promotion on the front page..