I'm still not certain I get your point.
Emovieposter this year has sold copies for $322, $805, $1,074, $624, $526, and $602 with the $322 copy being listed as fair to good and the others being listed as nicer.
Looking at closed ebay auctions I see sold prices of $775, $595, $510, $500, $500, $495, $450, $449, $341, $300, $300, and $279.
As you would expect the $279 is heavily worn and the $775 is very nice with the others being somewhere in between.
So there is obviously strong demand for this poster - ebay averages a sale a week and Bruce sells on average almost one a month and they continue to bring strong prices as condition warrants.
So your point is that because it is so popular and there are enough to find these buyers it should sell for less?
Shouldn't the argument be, thank goodness it's not a rare poster, because with this kind of demand the prices would be through the roof?