Child care in San Francisco, the kind that goes from 8am to 6pm, runs over $2500 a month. That's not ultraluxe, that's pretty standard fare, and my estimate is probably on the low side. A 3br house in an unfashionable but largely safe part of town is probably well over $4000 in rent. Again, that's not a high estimate. If you have 2 kids in daycare and are paying a mortgage or even just renting, you're looking at $9,000 a month in these expenses alone.
Wealth in San Francisco is more measured by when you got into the housing market than what you make, salary-wise, unless you're quite a ways up.
Now, a two income family with tech jobs is likely going to have at least 300k in family income (though even with the expensive 8am to 6pm day care, expect lots of phone calls coordinating who will scramble over to day care before 6). These families are not "scraping by", and I agree we need to be careful with hyperbole. But the median household income may not reflect the cost structure for new arrivals to the housing market who lack the family structure that would cushion the blow of daycare costs.
