Berlin is a very large city. This article covers two districts, Friedrichshain and Kreuzberg, which are experiencing a boom that is starting to raise the rents from insanely dirt-cheap to something people outside Berlin would consider "normal".

As it turns out, those two districts also happen to be the most trendy in Berlin. There are many other districts in Berlin that are not affected. For example, I haven't heard much about a rent crisis in Wedding, Alt-Moabit, or any place outside of the Ring-bahn.

To put the "crisis" in Bay Area terms, it would be like if it were impossible to find a place to live in the Mission, even though you could still get a place in the Panhandle, and therefore there was an article about a rent crisis in San Francisco, ignoring every other district in the city.