I'm curious about the algorithm. Is there a ceiling for book prices? I seemed to get very similar results for multiple different types of books, including being offered $3.21 for one that sells for $100:http://www.amazon.com/gp/aw/d/0575066601?pc_redir=1405401886...
There is no ceiling in place (I need to look into why different books show similar results). For the mentioned book, there's a difference between for how much it is offered and for how much it is bought (if someone wants $100, it doesn't mean that anyone is buying it for that price)
Scanning 44 other book-buying sites, only 3 are buying that book and the price is between $0.12 and $3.97