At&t's 24 month plan is also 75%. They do have a plan where you can upgrade after 12 months but it's a 20 payment plan which means higher money payments.
Also Edge is way better than contract if you have a 10 GB plan or more. No way anyone that as a 10 GB or higher plan should be doing a 2 year contract. Of course best way is to just pay for the phone in full( if you can ) and getting the month to month discount.