If that price is accurate, then $15 for a 1 1/4 lb. lobster at a restaurant is actually a very good deal. No doubt its cheaper if you buy it at Fairway, but its cheaper at any supermarket as compared to a restaurant.
I picked up 2 lobsters at the Lobster Pound for 8.95/lb a couple of weeks ago, which is about a buck cheaper than Fairway. Very good quality. I don't know anything about this Buttermilk Channel thing the OP is referring to though. Is it some kind of special cookout?
The Red Hook Lobster Pound lobster is a Friday night special at Buttermilk Channel. It is in addition to the regular menu. Both my son & husband have had it and loved it. I'm not sure about the pricing.