If your books are print - on - demand with high printing costs, you may not be making money off this. (castlegatepress.com)
Compare that to vanity or even traditional publishing royalty rates of between 15 - 30 % after the wholesale discount, higher print cost and then the publishers cut. (bookcovercafe.com)
With relatively higher Print On Demand (POD) costs, the system is not sustainable. (castlegatepress.com)