I think that’s more due to the relative attractiveness of the cities. London, NYC, Paris etc have become extremely expensive because they’re world cities, attracting huge amounts of people and jobs. That’s not really the case for Vienna, or Glasgow, or Riga etc

In fact Vienna has had a huge population growth in the past 20 years

Fewer people than 100 years ago, compare that to Bay Area. https://en.wikipedia.org/wiki/Vienna#Demographics

100 years ago there were 4 families in the now single apartment I live in. There was an extreme housing crisis and the current system started then as a direct response to that extreme overcrowding.

Bay Area could learn a lot from Vienna. Especially about building up.

How many new units have been added over the last 20 years?

Not sure exactly but the population has grown from 1.5 million in 2001 to 1.9 million in 2021 Some of that growth fit into existing stock but since the late 90s there has been a lot of new neighbourhoods built. The city generally plans ahead, even building public transport like metro out before it is completely needed.

E.g. out to this new neighbourhood

https://en.m.wikipedia.org/wiki/Aspern