In LA, from Chinese owned AT&T authorized dealers, you can usally get about $200 (more for higher plans) cashback for signing 2 year NEW contract if you don't take a phone. (renewing won't get you much benefit as the store don't get much commission for renewing existing customer)
If you ask for a non-carrier (non-subsidized) phone, like N97 in this case, they can get you the phone for phone price - $200 (or whatever cashback you can get).
If you ask for a subsidized phone, you can even get better deal.