Unless they're counting stock gains. In which case that could easily be a SWE. Netflix lets you choose your stock/cash ratio in your comp, and if you went stock heavy you could be at $3M a year if you've been there a while.
I don't get how people in SV can make this much and not be financially set after a few years of working.
That house will cost $2M at least if you want to be near the office, which means, assuming you can collect the $400,000 down payment, will leave with a mortgage/tax/insurance payment of about $9,000 a month, or $108,000 a year. The tax man will also take about 1/2 of your earnings.
That leaves you with less than $200,000 a year. You'll spend probably at least $50,000 on food, clothes, activities, etc for the kids and yourself.
So now you're saving $150,000 a year, if you're super frugal.
Let's assume you're ok with retiring out of the Bay Area. You'll still need a couple million to retire on. At that rate, it will still take you decade to do it.
All that being said, I have a friend who did exactly that. He worked as a senior/principal engineer for about a decade, was single the whole time, lived super frugal, and retired back to Kansas. I hear he just sits at home working on open source, going to the bars every night.