Instead of receiving a 25-cent, 50-cent, or even a dollar royalty for each copy of your book sold, a self-published author can earn 40 to 60 percent of the book's cover price and sometimes even more. So, if your book sells for $15 per copy and you sell just 1,000 copies, the profit is between $6,000 and $9,000.
Conversely, if you're an author whose book is published by a major publishing house, you earn only a 25-cent royalty per book. If that book only sells 1,000 copies, your earnings are a mere $250. As initial sales are generated from your book, you potentially have to repay your outstanding advance to the publisher. (If the book doesn't sell, however, the advance doesn't need to be repaid.) Even if that's been done, your literary agent often takes between 15 and 20 percent of your earnings as their commission. If the major publishing house sells tens of thousands of copies of your book, as the author, you stand to earn a decent income. This, however, doesn't always happen.
Another benefit to self-publishing is that you don't have to wait three to six months to receive royalty checks from the publisher. Authors who have their book published by a major publishing house often have to wait for the money they've earned, but self-published authors tend to be paid a lot faster, especially on copies of the book they sell directly to customers. Self-published authors also aren't subject to a withholding of royalties as a reserve against returns for up to six additional months.
As a self-publisher you stand to earn more money per copy of your book sold, but it's also considerably harder, but not impossible, for self-publishers to get distribution in major bookstores.