I thnk 4000$ for 3 onths should do you just fine. Just watch the partying, thats where money can be blown with out think, and before you know it,...NO CASH...
I think half of these cities are really expecive
London, Amsterdam,Munich, Paris, Rome,Venice, Florence
The rest "should" be a little more affordable.
Dont sell urself short either, go out on a lim sometimes and treat urself 2 something nice...dinner or show or something.
I surrvived on canned tuna and bread for almost a week and a half in the UK, and it was not that bad.
I am sure ur going to have a great time!!!!