Cool concept, but the books I compared were 20-50% higher than Amazon, and they charge another $3.50 to ship in 7-10 days.
I'd argue that buying from Amazon has some externalities that aren't captured in the price (particularly in their treatment of labor). I pay more for some times of food that avoids things I consider negative externalities, I'd do the same for books and other commodities. That's just an opinion, though, feel free to disagree.
Also, do we know for sure the Ingram warehouse employees are better treated than Amazon?
Disclosure: I work for a child company of Ingram