A) Students educated in Berlin are far more likely to move to other cities, since there are e.g. no jobs in production. How many engineers working at Daimler did study in Berlin (i.e. costing the city money, without contributing by paying taxes)?
B) A lot of large companies are currently opening offices in Berlin. They are gladly using the services of the city, as are their well-payed employees, effectively raising the rent. However, they will still pay taxes at their headquarters in a different city.
As I said, I have no numbers on this, but the situation is way to complex to just say that Berlin is wasting tax money. It certainly is - in a lot of areas - but so are others states.
Instead of being pissed that Berlin is trying to improve the situation and keep the city affordable for everybody, maybe we should start asking how we can achieve the same in other sought after locations as well.