Well, since my Aunt Barbra and two cousins all set pots out, I don't have to pay "market price" very often.
But Mables Lobster Shack (Mables Lobster Claw) in Kennebunkport was nice. Some may say a bit upscale for a lobster roll, food is good, their peanut butter ice cream if you still have room for desert.
"Steamers" are available most everyplace. Crab cakes are superb, and a personal favorite.
Hit the side roads leading through coastal towns, look for cars. The locals know where the best/cheapest/freshest seafood is. In reality, anyplace near the water will be a winner.
Rick