I got my Charge on Costco.com. After watching phone prices on four of the newest devices at that time, they were the one that reduced their prices first by a long shot. You can also buy your phone on a phone's upgrade discount, then switch your new Costco phone to any other phone you want. Costco said i could even sell it if I wanted, as long as I bought on an eligible upgrade, they didn't care what I did with the phone once I got it. No waiting 180 days like Amazon or wirefly to change your phone to another phone. Costco also usually throws in a few free accessories.
There are countless other resellers to look at including local ones that don't have an online presence. What is or isn't cheaper depends a bit on which devices you're specifically considering. Don't overlook existing threads.