This Warehouse 23 GURPS Classic Bundle is a nice deal.

Twenty bucks for five (out of ten) random pre-Fourth Edition GURPS books is a bargain, especially since I can say from experience that they’re all worth picking up.  And I am going to guess that if you shell out the forty bucks then you might be able to sweet-talk Steve Jackson Games into giving you all ten with no duplicates. At the very least you can ask: the worst that they’ll do is say “No.”