I worked in one... engineers didn't work quite that much but about 60 hrs a week. Saturday a full day is standard all year around. The peculiar thing was that right next to our cubicles there was a level 1 phone tech support team. Those guys worked exactly 40 hour weeks. Or team of test engineers were paid $600/month. The tech support guys only $400. I would often ask the engineers if they were cool with the fact that they made the same pay as a phone guy but had to work much harder. At first they were all puzzled, then I'd point out their hourly wage. They all would respond that it didn't matter, it was about social status. Even some of the ladies working in designer bag stores made better pay than them, but didn't have the statis in their view. It kind of blew myind, status means nothing to me, but I am considered eccentric. Anyway, thankfully my base pay was higher than both groups due to nationality.
My friends who work those hours make well over double what I do from their bonuses. They work these hours because they do datacentre builds and these cost the company a fortune for every day. Doing anything to shorten them is worthwhile and it encourages the type of people who'd work in the oil fields.
There's no way a FAANG could hold onto staff requiring 72h/w without paying huge bonuses.
Working 72 hr/week while making $200k/yr is only $53/hour.
To get to $80/hour would require a salary of $300k. $100/hr is $375k. Oh, and taxes because not an owner of capitalist assets.