We've seen London prices drop recently. That's mainly because we've seen higher interest rates and a flight of capital from the UK. People aren't as confident in the ponzi scheme continuing. It may also be in part because of huge drop in population post-brexit, although AFAICT there are no accurate numbers on that because the government doesn't want to admit that Brexit is a disaster.

I would guess Austin might be seeing a drop because it was "the big thing" for a while but now the consensus is it is not going to rival San Francisco. The rent seekers are moving elsewhere because there are bigger capital gains to be made? Just a guess, but you can probably verify it by checking house prices in Austin vs San Francisco.

In Austin, it's because they are building a huge amount of housing!

Like yeah, it probably is less profitable to speculate on housing in Austin, where pricing is improving because of increased supply, you need to do a little more than hand wave of your argument is that the causation goes in the other direction.