This is a Washington Post article that starts out as a standard, "Self-Published Author Gets Rich!" story (they even use the phrase "gold rush" in the title, gah, despite a long disclaimer in the article that, no, sorry, most authors don't get rich by writing). Eventually, however, the article gets more interesting, because it attempts to analyze how e-book consumers behave, which is kind of an unknown at this point.
The article points out that romance readers tend also to be insatiable readers. As a result:
New marketing patterns of lower online prices and impulse buying created a perfect dynamic for authors like [romance author Nyree] Belleville: Genre authors who were prolific but who had not been too successful. This peculiar level of accomplishment meant they had written books for print publishers, seen sales vanish and had the rights revert back to them, and even had completed manuscripts that publishers had rejected.
This left with the writers with just the right recipe: a small but devout core audience; a readily available backlist for new readers to discover; a knack for writing fast; and an inherent appeal to a fan base that read voraciously.
Joe Konrath is a big believer in having a lot of titles out, and Bellevue's experience certainly supports his argument: Because of her speed and stash of completed books, she put out 12 books in 18 months. I will probably put out 12 books by the time I die. But you know, something? I'm OK with that.