Weve just received a tip that IceMonkey.com is selling the GSM version of the Samsung Galaxy Nexus for $520, inclusive of shipping. There are limited quantities, so you might want to hurry up. You can get the deal here.
Update: Or, as QuantumRand in the comments has mentioned, you can get it from Amazon for $525 (with shipping).
I must mention, though, that I cant vouch for the website. This is the first time Ive heard of it, so Id prefer that someone whos dealt with the site before mentions his/her experience in the comments.