I think xenok nailed it with his segmentation of entertainment activities: event-based is going to be more expensive no matter where.
As per the budget difference EU/US-UK, I think it comes down to two drivers:
1) Much more friends- rather than event- based entertainment --no need to have motive to hang out, importance of home-based activities.
2) When going out, much lower per-capita consumption (one, max two beer/wine glass/cocktail*): saying 3 beers per 2-3 times a week sounds really weird.
Since I began working, event-based entertainment ramped up a lot for me**, as well as, accondingly, expediture. I believe, though, that friends-based (then cheaper) alternatives could regain lion's share in school.
The different attitude to saving and debt also have a say in this.
* I studied in Scotland for one year in undergrad. First night there, I went out with some colleagues and a Professor. We sat and ordered a beer. 5 minutes later, I barely took a sip, nursing my drink Europe-style, when I was apostrophed by the Professor:"What are you doing? Come on, finish it as we are moving to another bar". This little anecdote pretty much nails it!
** I also believe: the stronger the connection with your associates, the less the need for event-based entertainment. The stronger the will to form new connections, the more the neede for event-based. This may explain why MBA budget could be so generous.