Great summary of cost of living and tech scene from maxklein. You can live very cheaply here, if you work at it. Some bars serve a half-litre of beer for 1€, some reasonable apartments can be got for 120€ a month if you can live with coal-fired heating.
The other tech company I know well is SoundCloud. They are great. They are mostly Ruby-based, but they're expanding the technology they use rapidly at the moment, so they might be flexible.
Good luck: Berlin is a fantastic place to live.