Many (all?) of the books listed on Amazon, are priced by the book seller that is selling the book, not Amazon. Book sellers can open an account with Amazon and use the Amazon website to advertise their goods, similar to how eBay works, except it's a set price, not an auction. You pay Amazon, Amazon keeps their cut, bookseller mails you the book.
And I agree, many of the book prices are absolutely nutz.
-Ron