The important context here: The conservatives who were at the helm pre 2004 created a big banking crisis that brought Berlin on the brink of insolvency, which forced the state to sell a bunch of public property: https://de.wikipedia.org/wiki/Berliner_Bankenskandal (German only, sorry)

> In 2004 the state of Berlin sold 65000 flats for 405 million euro.

So, the average price per flat was € 6,230. That sounds impossibly low. Or were these distressed, dilapidated properties?

In the same period or a bit earlier, hundreds of thousands of apartments in Bucharest and other major cities were sold at preferential prices (read: heavily discounted) to the renters. It was a populist measure, people bought apartments and sold them a year later at 4-5 times the purchase price.

Also the old Communist era small apartments were cheaply build and without much value. 6000 euro looks low, but I bought in 1998 from the open market an apartment for $13,000 (the transaction was in USD). These days, that apartment is around 3-4 times more expensive (I don't have it for many years), but it is still small and poorly insulated. "small" means less than 50 square meters, one living room and one bedroom.

Back then the general sentiment was that Berlin was going to shrink. A lot of high-rises were razed in the eastern districts, others were converted into low-rise buildings as part of the "Stadtumbau Ost" program.