If you are a customer and have no existing contract, why aren't you eligible for the fully subsidized price by signing a new contract? In my experience, such a customer is eligible for the same perks as a new customer since they're pretty much in the same boat, except for the existing phone number. There's nothing holding you back from canceling and porting your number elsewhere.

Some people have been doing an end-run around this issue by joining with a new customer account and then canceling the new phone number while porting/transferring the old one. It's a little more time on the phone, but you get the phone at the price it should be for new contracts.