I remember reading or hearing something a few years ago that said only 10 percent of all books published ever sell 1,000 copies or more. I cannot seem to find exact numbers anywhere, however, I found a boatload of other statistics on the Para Publishing website. The self-publishing numbers are pretty low ... only 3.4 percent of Xlibris copies have sold more than 500 copies, for example.
So when I recently hit the 1,000 mark with "The Developers," I have to admit, I felt pretty happy about it. True, I haven't sold every single copy. Some of them have been giveaways for various events. The point here, though, is I've spent roughly $100 on advertising. Now, think about how much large (and even mid-size) publishers spend on advertising, whether newspaper, magazine, TV, radio or online. You would expect those books to be more successful, but how much more successful?
From the Para Publishing book statistics page, a "successful" fiction book sells 5,000 copies. To me, this means the book actually made a profit. That stat seems to be inline with what I would suspect, although I could probably turn a profit selling 50-70 percent of that many copies. Then again, my calculations could be wrong because I would have to print more copies!