In reply to koolkat:
Large sellers on Amazon usually use software that manages their sales and inventory, and which interfaces directly with Amazon's platform. This software monitors prices on the site and adjusts the seller's prices to maximise return. These insane prices, like the Messner book, happen when two or more seller's systems get into a high-speed price war and start automatically bidding each other up.
For an extreme example, google "$23.6 Million Dollar Book".
Andy