Quite possibly one of the rarest atari games ever.
I was watching G4's Cinematech special on rare games, and I was originally going to leave because I didn't like that show. I'm glad I stayed.
They showcased a bunch of rare games and their going prices. Like the Zelda CD-I trilogy, in range of like $50+.
You what the most expensive one was? This old atari game, with no definitive name, sometimes called Pepsi Invaders or Coke Wins. It had no cover, and it was given only to Coca Cola employees. Only 125 are said to have been made.
http://www.atariguide.com/9/904.htmAn ebay auction showing it went for $1800+