It’s still not quite SF or NYC or London prices, but it is much more in line with the rest of Germany now.
It's been my impression from the two or three times a year that I'm in Berlin for a few days that it just works very differently, there's a trade-off between cost of living vs convenience that people accept when they move to Berlin. It's dirtier, a bus or train may just break down, people are generally a bit more rowdy, and you don't expect much from the administration, but then again: you pay a lot less, so it's worth it, like a hostel compared to a hotel.
https://www.statista.com/chart/15738/the-contribution-of-sel...
https://qz.com/753244/berlin-is-the-only-capital-city-in-eur...
Berlin is quite a unique capital in that it's relatively poor and contributes relatively little to the national economy. Apart from its size warranting certain infrastructure with sufficient capacity, it'd be surprising if it had much better infrastructure than it does. Its economy doesn't easily allow it.
Berlin can be cheap relative to other capitals (though this is getting less true) but the extent to which that's the case depends on your personal choices.
Public infrastructure is another matter because it serves everyone and everyone contributes - there needs to be a minimum bar. And yes, if I pay the same taxes as everyone else, I want a comparable level of service and convenience in my infrastructure to what people in the other cities get.
The taxes aren't the same as well - local infrastructure isn't a federal issue, so federal income tax doesn't pay for that. Berlin's tax factor for companies (a major part of local taxes) is 410%, compared to Hamburg's 470%, Munich's 490% or Cologne's 475%. Berliners have decided to go with lower taxes to attract companies away from other cities, so Berlin has less money to spend on public infrastructure, even though Berlin gets a lot of subsidies from other states (2-3bn/year).
This is part of Berlin's unique culture, though, isn't it? Usually, the capital cities aren't also average to below average in living costs, which Berlin is. Berlin isn't convenient, Berlin is dirty, raw and cheap.