I got very sad that I just found this out at the end of my interchange year, so I hope it helps the next ones.
The Goethe Institut is an international well known institution that promotes the culture and the german language. Here in Bremen it is located at the Universität Bremen and the regular price of a 4 weeks course (5h per day) is 1.040 euros. The price, however, is the half for Hochschule Bremen students (520 euros) and it becomes even cheaper for Uni students (around 150 euros).
I did the B1.2 during the entire month of May and it totally worth it!
If I've known that Uni students had so much discount before I wouldn't choose Hochschule (really!).
I don't know how does it work in another german cities, but I think it is the same.