Complete Folio of Birds: 19th century,$1.8 million
Do you like pictures of birds? Do you have 2 million dollars? Then this is is the book for you. It's actually darned cheap, because, of the most expensive books ever sold, the fifth, sixth, and seventh are all copies of Birds of North America (each one sold for between 7 and 12 million). That's no surprise though, because everyone knows how difficult it is to find drawings of birds.