Klartext
Klartext have some very reasonable prices and come highly recommended by people, particularly for the beginner and mittelstufe levels.
Prices: All courses last 5 weeksMorning Classes (20 hrs/wk, 5 d/wk) €330Afternoon Class (16 hrs/wk, 4 d/wk) €260Evening Class (5 hrs/wk, 2 d/wk) €100
http://www.klartext-zentrum.de/
See also:
German language schools
Munich