Looks like the GoPhone lineup has been slightly adjusted. There is even a phone with the new AT&T logo on it now...
The Motorola c168i, which looks to be the Compal imitation of the SLVR or, more closely, the Motorola L2, is $40. Not bad for a decent, decently thin phone. And this one actually has polyphonic ringtones. Though you're really not buying from Motorola (you're getting a slightly different user interface) when you buy this one.
The Nokia 2610, at $80, costs twice as much for what look to be similar features. But hey, it's a pretty new phone, its a name brand and you can't go wrong with a Nokia so whaddya expect?
Oh, and you can get the new (ish) Pantech C3B for $90, which is basically the C300/C3 but with changeable faceplates and both silver and blue faceplates included. Nice little phone, but it sure is little.