Edit: And I was right, haha.
While London is one of the most expensive cities in the world, Berlin is cheap for German conditions. At least the parts that haven't been gentrified yet ;)
Berlin is really cool and has lots of alternative people and seems to be the only german city with a bigger start-up scene, but it's poor AF. I'm living in Stuttgart and while I prefer to hang in Berlin, the money is in the south.