No, haggling isn't expected and would probably be a bit odd. Or, rather, I would say that you shouldn't plan on haggling any more than you would if you were buying art from any other art dealer. Maybe someone would give you a discount on merchandise if you asked, but most people come in, find what they want and pay the price on the sticker. It's a well respected establishment that has been around for over 25 years. The artists they represent are, in many case, well known. You will get the vibe as soon as you walk in the door.