Even if you want to upgrade within 2 years you will not receive full discounted price on the phone. I don't see why Nokia would release a phone that works only on Tmo's 3g if they didn't have something brewing. How is it cost effective to subsidize though, maybe it makes sense if you're cheap and you don't want to pay a large chunk of cash up front but in the long run a subsidized phone on a more expensive plan is not a logical choice.