Looking at the Case-Shiller index for SF, I would agree it looks speculative.[1]

SF home prices went from an indexed 219 in Mar 2006, down to 120 in May 2009. That's a 45% decrease over two years.

Right now the index is at 259 and that's inflation adjusted.

[1]https://alfred.stlouisfed.org/series?seid=SFXRSA

I believe the Case-Shiller index is "seasonally-adjusted", not "inflation-adjusted"[1]. What makes you think it's adjusted for inflation?

[1] https://www.advisorperspectives.com/dshort/updates/2018/03/2...

The question also is, have sales kept up at those values?