One Way RV rental ?

I am planning on taking a one way trip to Phoenix AZ from Seattle WA at the end of May. I have looked around and found a couple of sites that offer one way rental, wanted to see if anyone here had some additional info on getting a good deal on one way trips, I have heard about companies that will charge less if they need a vehicle moved to a specific location etc.

Any info would be greatly appreciated..

Thanks,
-Lee