I do agree that this introduces the BATNA situation later - but that's so general that I actually can't think of any reason that isn't considered "BATNA" for why the dealer should never accept less than $50. Maybe I just need to open up to more creative situations: the Mafia mob wants to keep table prices up and so threaten to shoot him if he sells it for less than $50; or the government decides that a fixed Table Tax was necessary so that each table was taxed $50 regardless of the price it was sold at; or he wants to signal that his goods are of high quality and so considers any price less than $50 to be too low for his store. Okay, on second thought this has turned into a pretty good example of why I should never say "I can't think of any examples" without at least first trying to think up some examples.