A 40% ratio for the $125,000 household would give you a maximum purchase price of $830,000, which would be a conforming loan in the Bay Area, not a jumbo one.
https://www.zillow.com/homes/recently_sold/house_type/
In the South Bay near Mountain View, there's basically no single-family homes under $1.5M, and the majority of houses go for $2M up. Many are in the $4M+ range. You can get cheaper in San Jose ($800K-ish for a run-down 2BR from the 50s) or Daly City (low millions), but most of the Peninsula and SF has a floor at a million.
Most Bay Area residents just don't own homes. They rent permanently or maybe own a condo. But the context for this sub-thread is "people with a house", and basically all mortgages for single-family homes are jumbo if you're not paying in cash or putting >50% down.
Buying a house for $1M is firmly middle class status. True lower class people simply cannot afford to live in the Bay at all.
To be in the top 1% in the Bay Area you have to make close $1M per year.
https://www.cnbc.com/2017/06/14/how-much-you-have-to-earn-to...
I've wondered recently how much of this house price inflation is because of cash buyers from China vs. cash buyers because they sold their stock in a unicorn vs. dual-FAANG-engineers with a mortgage vs. people who leveraged up to the hilt with 3-5% down adjustable mortgages. ChuckMcM posted county property records a couple years ago that suggested the former category isn't actually a big one. The first 3 categories are relatively insensitive to downturns. The last will get hit hard this recession. If most houses are owned by people in the last category, the effect on housing prices will be much more dramatic than if they're folks sitting on houses with no mortgage.
The average person with a house in The Bay probably doesn't make as much money as you think. They mostly have very high debt to income ratios.