Fuckers.
Interesting, do you have another provider in the area?
I think a lot of the negotiating power comes from the ability to threaten to switch to <competitor>. If they know there is nobody else (and in many places in US there isn't), they can often say "yeah sorry to see you leave", knowing that you can't really go anywhere.
I have for example been oscillating between two local providers. Both have equipment on "premises" installed and just have to switch it on and off. So as soon as one ends promotions, I switch to another and do so on. Sometimes they give me the promotion rates back without having to go the full switch around the circle.
Promotions usually run 6 month to a year.
Take my service for example. $40 standard rate (promo was $30). There ain't no bundle out there that runs $40 once the promo period is up.
Its possible that you would achieve the same with BH, but at least ATT hates when you mention competitors, and they make so much money that they would rather make less on you, than lose you big time, knowing once a customer is gone, his/her re-acquisition is very expensive. At least this is my experience. I had an impression that I could push it even harder and call again, complain and they would lower my bill even more before finally dropping me for good, but I am already satisfied with my plan.
Edit: tl;dr - always bluff with your cable provider that you drop them b/c they are expensive and see how far you can get. Most likely your $150 bill can be cut 50% and they still will make money.