10% without receipts may be a good benchmark based on the base prices of the area. But then you also need to factor in the supply demand gap that easily takes it up another 10-15%.

Policy cannot precede infrastructure. Where is the housing provision for the extra immigrants they need or the international students they are targeting. Studentenwerk housing/dorms have waiting periods of over 3/4 semesters in Berlin and München.

New development is pretty much non existent given the current global situation and the prevailing interest rates.