Part of the point is that if you own the product you get 100% (well, more like 95%) of the income, rather than the 10% you might get via royalties. 1000 sales for a nonfiction book is a solid year's income.
True, but the 90% that you don't see through a traditional publishing arrangement doesn't go up in smoke - it pays for marketing, distribution, accounting, and a bunch of other stuff. Now, historically publishers sometimes rip people off. But the problem is that by focusing on that narrative (especially in the music business), we have collectively thrown the baby out with the bathwater in many cases, overlooking the fact that authorship and publication are often entirely different fields of competence. Some authors are also good at publishing - and more power to them. But economic efficiency is maximized when actors specialize in those fields where they have a comparative advantage; if you're a writer, it's not really a good use of your time to be organizing your own book-signing tour unless you really enjoy that aspect of things.
