On the other hand, it is hard to believe you can rent a
200k€ place for 500€/m. In Warsaw, a 2-room 40-50 m²
apartment in the city center costs about 400-500€/m to
rent, but if you wanted to buy it, offer prices start
below 100k€.
There are places that are unusual (like Mitte - the center of the city), but for ~90%+ of Berlin the pattern I described above more or less holds.
Even if you saved that 100-150 euro every month,
you'd not afford buying it after 30 years, assuming
it stayed at the same price-point.
If you're in a position where you have extra money and you can choose whether to invest it in the stock-market, buy a nice car, or put a down-payment+mortgage on a place to live it's a different consideration.
This is the point I was making: renting is the only choice if you can't get a safe mortgage with good terms. And getting a mortgage with monthly payment X, when you could hardly pay more than X would be a very risky option and even if some (crazy) bank agreed to it, they would set a very high interest rate for covering the risk. But getting a mortgage with a monthly payment X when you can really afford 4X is a totally different story.
While Berlin is a bit special case with its housing supply, renting is actually crazy expensive in Poland. You should compare the prices to e.g. Lithuania or Estonia, the difference in affordability is mindblowing.
On the other hand, it is hard to believe you can rent a 200k€ place for 500€/m. In Warsaw, a 2-room 40-50 m² apartment in the city center costs about 400-500€/m to rent, but if you wanted to buy it, offer prices start below 100k€.