If you're eligible for a n upgrade, you should be able to utilize Walmart's holiday deal on iPhone 4S -- $47.00 for an iPhone 4S, $127.00 for an iPhone 5.
yah if you cant do the replacement my friend just sold his att 16gb on cl for $280.. prolly coulda got more. seems like verizon ones go for less than ATT too.. so 250-300 price range