You read the title of this post correctly. Every book at Desiring God is $5 "while they last." If I might make a recommendation, I purchased the Festschrift for Piper, For the Fame of God's Name when it first came out and I paid over $20 for it. It is a beautiful hardbound book over 500 pages in length, and the fact that you can get it for $5 is almost a sin. They also have another large Piper book, What Jesus Demands From the World, for only $3.
Well I said it, now you can do what you will with such information.