"That's the wrong question to ask. The question is: how many writers prior to ebooks could quit their day jobs and live off their writing alone? Answer: not many. Out of the hundreds of writers I know, less than ten percent can make it without supplementary income. If I discount bestsellers, the number is much smaller--I just happen to know a lot of bestsellers. I'd wager that more writers can make more money self-pubbing than legacy-pubbing."
Although I will not take Joe up on this wager anytime soon, I don't think this question will be resolved effectively due to the multiple variables involved in the comparison. Nevertheless, I do believe there is a fundamental asymmetry in self-publishing compared to legacy publishing that tilts the scales in favor of the self-published writer. In legacy publishing you compete with other aspiring writers for acceptance by a publisher, and if they take you, then you compete against other published writers for readers: in other words, a double hurdle. However when you self-publish the first hurdle is gone, and you are left just with the task of reaching your readers.
What do you think?