Also, the real estate investors are buying up property and keeping it off the market, to prop up the remaining prices. Or sellers refuse to put empty buildings on the market, and let charities turn the empty commercial buildings into cheesy "social centers" or "fairtrade markets" or "quit smoking clubs" that nobody goes to, just so that they don't look empty. For a while, housing all of the refugees helped (that's actually why Germany wanted them: to prop up real estate prices), but they are already housed and the citizenry wants them to go home, so some of those houses will come back on the market, soon...