Sorry if this is the wrong place to post, but I thought some of you would like this information.
I was able to rent the set of 8 strategy guides from Campus Book Rentals for about $70 (including shipping).
The rental period is 130 days, so if that's enough time for you, then I think renting is the way to go. I rented in early February and took the GMAT on April 23. The guides were very helpful! (I focused more on the Quant guides and really only glanced at the Verbal guides...)
This link is for the set of 8, however, I think you can rent individual guides as well.http://www.campusbookrentals.com/book/098417804X/Manhattan-GMAT-Set-of-8/Manhattan-GMAT-Prep/9780984178049/
P.S. In case you're wondering: I am in no way affiliated with Manhattan GMAT
Prep or Campus Book Rentals. =)