There is enough new housing here that apt buildings went down in monthly cost last summer. People keep moving here so house prices have been stubbornly resilient.
According to this, Seattle rents doubled from 2010 to 2016 and have been fairly flat since then. SF seems to follow basically the same curve: up 1.5x from 2010 to 2016 then flat-ish.
Maybe I was too much on the dropping side but the article says prices had been booming like you said for a decade and 10k units were filled and then prices stabilized.
https://www.rentjungle.com/average-rent-in-seattle-rent-tren...
https://www.rentjungle.com/average-rent-in-san-francisco-ren...