Cosmetic condition is going to play a roll as well. Nobody is going to pay high dollar for a phone that looks like it's been through a gravel pit.
Well I can honestly say that there isn't a scratch on it. I've been using a case and screen protector since day 1. Just recently changed case to the Barely There Chrome w/Mirrored screen protector.
LOL right before the 3G came out, I sold my unlocked and jb'd 1st Gen iPhone for $445 on eBay. It was amazing. It not only paid for the 3G I got, but etra to boot. Not a bad gig. I love my 3G now, I'm waiting until June see what apple introduces, if not Im totally fine with the 3G for a while as I am jailbroken, and love my jailbroken apps like QuickReply and MyWi
I sold my 3G 16gb on ebaY for $415 and 2G 8gb on ebaY for $320 recently...the phones were JB and unlocked in Mint Condition with all accessories and the DESCRIPTION was SUPERB which plays a vital part in how much u get for your phone so make it count