I’m going to let you in on a source for cheap role-playing books: Paperbackswap.com. Like the name implies, it’s a website that abstracts swapping books. You list the books you no longer want and create a list of those you do. As people request books from you, which you mail off to them, you get credits, which can be spent to get the books on your wish list or you find via browsing. Think of it as turning one book into another for the cost of packing and postage.
In addition to my fiction and non-fiction reading, Paperbackswap has turned out to be a resource for picking up role-playing books on the cheap. Plus, a couple titles I threw on my list for fun — GURPS Technomancer and GURPS Voodoo — both appeared. Battle-worn, well-loved copies, but still there. Most of what I’ve picked up are GURPS supplements, but I also acquired Uresia: Grave of Heaven.
There are, however, two provisos. This is not a speedy process. Most of the role-playing books I’ve acquired through Paperbackswap sat on my wish list for a year or more before someone happened to list the book, or it became my turn to receive a copy. You have to be prepared to play the long game. It doesn’t hurt to have GURPS Places of Mystery in my queue, no matter how long it takes to show up, if ever.
Two, these books are typically not in collection-grade condition. In fact, if a role-playing book has gotten to the point that the owner is willing to list it on Paperbackswap, it’s probably seen a lot of action. Which can work out great, if it’s a title that normally demands high prices. You get the content with none of the worries about maintaining the book’s condition or feeling bad about how much you paid.
Paperbackswap isn’t a guarantee of getting cheap role-playing books, but it never hurts to set up that wish list. You even get two credits to start off when you sign up.