You're right about people will pay a steep price for something special. I went to Game 6 of the '09 Series when they clinched, and at that point, it was the highest priced event ever on Stubhub.
But, if you turn on a Cubs or Red Sox game, you won't see an empty seat behind the plate. Probably a bunch of other teams, too.
And, I'd say the difference between this and like you said other teams and concert events - is that this is 81 games you have to fill. You need all types of fans to be able to do that.