This is interesting to know...I was thinking about getting a book or two of Jill's.It depends on how amazon carries it. If you run a store through amazon where you ship the goods to the customer, vs an amazon store where amazon holds your stock and amazon ships to the customer vs amazon buying the books and selling them directly are all different, with decreasing profit to the publisher.
But a lot of diving books are hard to get through amazon for some reason. Jill Heinerth's books are available through her store but through amazon you mostly get resellers who mark it up.