If Rizzoli uses CreateSpace, then the book probably made some profit. But it's hard to do a trade paperback for less than $12 minimum actual cost, depending on number of pages, font size, interior art or photos, etc. pOD mass market paperbacks are generally not good quality, hence the trades and hardbacks.

So bookstores don't have a lot of incentive to carry them. Stores can't run sales like they do for a big publisher's book. Even for a big publisher, when a new hardback is half price? That's a loss leader.