De Humani Corporis Fabrica: 16th century, $1.5 million
You ever pick up a modern anatomy book? There's some pretty gnarly stuff in there. Now imagine that book minus half a millennium of scientific understanding, plus the creepy precision of renaissance etchings, and you have got yourself a pretty messed-up tome. Not enough squick for you? Well, Brown University's copy of this book is bound in human skin!