There are two Humble Bundles active for Pathfinder at the moment.
For those who don’t know Humble Bundle - it is based on a ‘Pay What You Want’ policy but you can unlock more stuff if you pay more.
So in this case you can get quite a lot of books (PDFs) for about 20 bucks.
The first one will expire in a few days and contains many rulebooks:
The other has just started and contains some comics: