I think there must be something cultural to it, because it's really not that watching football over here is cheap (the cheapest Man Utd season ticket I could find was £475 (~ $750) but that's for 19 games I think).

But then again, there's no salary cap over here and it's very much a free agent market, and you have to compete with the European teams which are either nationally bankrolled (why yes, Real Madrid, I am looking at you) or bankrolled by whole companies (i.e. Juventus is the Fiat team because they're the big company in Turin).