First Edition of Don Quixote
It would be quixotic to try to estimate the influence of Miguel de Cervantes' Don Quixote on the Western literary canon (see what we did there? Word play high five!). The tale of the chivalry-obsessed hidalgo can be found in any bookstore, and new translations come out every 20 years or so. But a first edition of the book, from 1605, is not so easily hunted down. The last time an original Don Quixote changed hands was 1989, for $1.5 million. You could buy a whole lot of windmills for that.