Just because you buy it, doesn't mean you have to wear it to the game. Of course you'll probably be able to get a much cheaper t-shirt commemorating the game from a street vender on gameday (I've gotten 3 shirts from street vendors at the Man Utd games in Philly the last couple summers). Of course, last time I bought a t-shirt commemorating an individual game before that game was Iran in '98....
You shouldn't buy it because the shirt is produced by Nike, an ungodly whore of a company only interested in getting rich off the backs (in this case literally) of soccer/football fans around the world. Yes, I realize every company is like that (I'm exaggerating a little bit), but I wish Nike could have left soccer to Adidas, a company with a real history in the sport and the brand all us old school players grew up wearing.
Because it's an ugly sack of crap. Does Nike actually employ professional designers of any variety, or have they outsourced that to little kids in the third world as well?