Take a look at http://www.ted.com/talks/amanda_palmer_the_art_of_asking.htm... TED talk, sheds some light on the how many people you need to make it big.

The industry launched her album, 25K bought it and it was a failure, on Kickstartet she raised 1.5millon dollars with almost exactly 25k backers. The irony, there are a lot of people and a lot of people like music, and even if its not the everyone, it's big enough that they can make a good wage.