Real math books that cost half a k

Hey, as the spring semester draws to an end and summer around the corner, the cost of books is a long distant problem for most college students. Oh, did you just see what I did there, I opened a bad wound, didn't I? Well, if you think you have it bad just imagine how you'd feel if your professor assigned you this Handbook of Set Theory? Yeah, as of this writing, this book costs $552.36 from Amazon.com and the best price is $503.99 usedon Amazon.com marketplace. How does a simple math textbook cost over half a thousand dollars?