I think this statement is misleading.
Publishing is the easy part.
Anyone with a few dollars can publish a book. Plus you pay the shipping cost to them, and from them when the books are returned. Bookstores and wholesalers, if you manage to get your books into them, are notorious for not paying or paying very late. A good publicist, to get you the media exposure and reviews you will need before those late-paying bookstores and distribution channels will even touch your books will cost you several thousand dollars. I don't want to turn people off from self-publishing, but neither do I want to say how easy it is to sell out of even 1,000 copies of a title.