I think it's hard to say. Depends on the phone, the plan, and so on. Not a lot of transparency in the process -- An unlocked iPhone is $650, or $27/month over the life of the contract. That would likely make up a big portion of the monthly bill, were it to be broken out separately in the statement.
Why? If you're in contract, you still have to pay for your plan during the entire contract. Even if you switch networks, they are still making enough money to recoup their subsidy cost. Effectively it just becomes a loan (with truly awful rates).
