Wouldn't this be wholly dependent on the distribution channel? I mean if you're going through Spotify and they're not paying you but beans, or iTunes isn't exactly working out, couldn't you...you know...use *another* service? The cost of reproducing the songs is nil given that it's already in a digital format, so it doesn't hurt to shop around.
I know they don't have a lot of popular support (last time I checked anyway) but what about services like Ubuntu One and Magnatune? Especially on the latter the payout model's pretty simple and straightforward. You could also say, "fuck it," and just put your stuff out on YouTube/ThePirateBay/Facebook/Google+/Wherever for free, with links to your event calendar for shows and something like Magnatune if they want to support you otherwise, maybe even a Cafepress/similar site for swag.
I'm not saying it's all the artists' fault mind you, industry execs are some evil filth, but they're not exactly lacking in options.