New cellphone upgrade offers are far from free

[Commentary] AT&T and T-Mobile have recently announced plans that let people upgrade their phones more often. But before you get too excited, you need to do the math.

With both the new T-Mobile and AT&T deals, it's possible to get a new phone sooner -- as soon as six months with T-Mobile and a year with AT&T -- and you might not have to sign a two-year service agreement. But you're still on the hook for monthly payments that could wind up costing you as much as or more than you're paying now. In the old model of paying a subsidized price, you actually get to keep your phone, which means you can give it to someone or sell it. But to find out the real price of any phone, you have to include the service costs, and that's where it gets even more complicated. It may take you several hours on the Web or on the phone to figure out your best deal. But considering the amount of money at stake over a two-year period, it's worth the effort.