Franklin Hiram King's book Farmers of Forty Centuries was self-published in 1911, and was subsequently published commercially.
In 1931 the author of The Joy of Cooking paid a local printing company to print 3000 copies; the Bobbs-Merrill Company acquired the rights, and since then the book has sold over 18 million copies.
These technologies technology make it possible to have a book printed or digitally delivered after an order has been placed, so there are no costs for storing inventory.
Print-On-Demand (or POD) technology, which became available in the mid-1990s, Print-on-demand was easy, since an author could simply upload a manuscript, choose an interior file format and a cover, and the book could be printed as needed, avoiding warehousing costs, and reducing the risk of being stuck with a huge unsold inventory.
These companies offer the cachet of being published and make the majority of their income on fees for intangible services paid for by the author in advance of publication, rather than afterwards from sales revenue.