What is the rarest LEGO set?

I think the rarest Lego set, would be the newest ones, that would be only on display for a while. There is NOT a rarest Lego set, that will be rare all the time!

Second answer: The rarest LEGO set is from the vintage LEGO Star Wars collection. The golden C3PO is pretty rare, and so is the Greedo minifigure.