You're leaving out out the dweebs who will buy both the standard and collector's edition versions of the game.....just to help pad the sales numbers. No.......I'm not kidding. I know several misguided individuals that bought multiple copies of GT4 when it came out. They claimed it was to have one as a collectable (still sealed) and one to play, but since all of these guys would go into torrid rages whenever you brought up Forza...I'd have to venture a guess that they were secretly hoping to win some kind of fanboy war/bet.
So, yes.........people are stupid.