I asked a similar question on Sega Age about a then $50 CIB copy of Earth worm Jim for Game Gear listed on eBay ( www.ebay.com/itm/331450516398 ) and it didn't even have the poster. That copy ended up going for $100.

I know the poster is very rare. Heck, all the complete pictures I have found on the net usually just show the game, box, and manual. Now I see this auction for just the poster: http://www.ebay.com/itm/231463163006

Ideas?