Good call.
I sent an email to Sothebys, along with some links, showing this poster had been printed, used in theaters & auctioned before as well as being available to buy for 59.99 from movieposter.com.
I received a reply back, saying that the info was noted and that they would look into this error and sale.
Nothing like that winning bidder paying about 50X+ what that poster can be bought for, let alone thinking it was something uber rare.