I believe these phones retail for $599 through Apple, and everywhere else I looked. Best Buy has them listed for $499 if you pay full price up front. Seems like a decent deal if you aren't interested in getting the new upcoming model or leasing the phone.
Note: I am upgrading so if I were to do the monthly installments, it would be $25 per month for 24 months = $600. New accounts can get it for $15 per month for 24 months = $360 so that would be the better way to go for new activation.