The average rent in Berlin (and other German cities) is not very high but that's because a lot of flats still run on a very old contract. If you're moving to Berlin, finding an apartment is incredibly difficult, even if you're willing to spend a lot of money. My grandmother lives by herself in a 90sqm flat in a really nice area and pays 400 Euros a month. In the last 10 years she tried to find a smaller flat (30-40 sqm) for herself but the cheapest she could find was 750. So she stays where she is and just doesn't use 2 of the rooms she has except for storage. In the meantime, a friend of mine moved to Berlin and couldn't find a decent 60sqm flat for less than 1400 Euros. The only way to get those affordable rents is either knowing someone who is moving out or getting super lucky by finding and getting it through a public ad.
Massenbesichtigung (mass viewings) are not uncommon. The agent will publish a public timeslot and literally hundreds of people lined around the block will show up to view a single flat.