> I'd like to believe even at FAANGs these mad salaries aren't common.
My impression -- as someone who is neither an engineer (anymore) or at a FAANG, but is making above the apparent market rate for technical writers in Silicon Valley at a company that needs to compete with FAANGs for talent and chooses to do so by offering high base pay and bonuses rather than stock options -- is that at this moment in time, these mad salaries are common in both FAANG and competing-with-FAANG companies, but only in specific fields and specific locales.
Personally, I'm not convinced this is sustainable any more than the SF Bay Area housing market is sustainable. If the shift to fully remote or "hybrid remote" workforces is truly underway, it's probably just a matter of time before that starts pushing down income levels. If you cut your cost of living in half by moving from Mountain View to Boise, employers will start factoring that into your compensation -- many already do.
In the long run, of course, that would lead to a slow creep toward equalization of cost of living across the country; there are already anecdotal (but loud!) reports of housing costs increasing substantially in surprising places as people leave the west coast and the northeast and move inland. Eventually that should make COL adjustments smaller or less common, but it will likely also make "I'm making $350K right out of college" less common. (Or whatever $350K is adjusted for inflation in a decade.)