In the US, dont you have the option to go onto 1 month rolling contracts, like in the UK?
I only ask as when my contract has ran it's time, I'm going to just buy the handsets from now on and stay on the £10 (about $16.30 US) a month roller, I worked out that regardless of the phone, (comparing to S3 and Lumia pricing) in 2 years I would have saved £200 approx. over having the phone cheap or free and tied into a long term contract...
When talking about postpaid in North America (other than a few exceptions) you pay the same price monthly whether you took a phone on contract or not. It's actually dumb to NOT buy a phone when you get an upgrade ever since they implemented prorated ETFs.
I can get a new phone every 2 years for $400 off and pay X amount of money per month, or I can buy the phone for full price and still pay X amount of money per month. I upgrade my phone at least once a year, but I ALWAYS buy a phone right when I'm up for contract renewal. Even if there is no phone I want from their selection, I will choose the one with the highest resale profit and sell it.