It's not, though. Median rent in Mountain View (significantly pricier than San Jose) is now $2390/month [1]. L4 total comp at Google, or E4 salaries at Facebook, is about $260K/year [2]. Average rent for a 1BR in Dallas is $1250/month [3]. Average total comp for a software engineer in Dallas is $110K/year. [4]
After taxes and rent, the Facebook/Google L4 is making $260K * (1 - 0.37 [5]) - 2390 * 12 = $135920/year. The Dallas SWE is making $110K * (1 - 0.16 [6]) - 1250 * 12 = $68939/year. Even with the $4K/month rents from 2019, the Facebook engineer is still putting away $116K/year, more than the total gross of the Dallas engineer.
People tend to underestimate the effect of the top-line on finances and savings. Eric Schmidt had a saying: "More revenue solves all known problems". It applies as much to households as to giant companies.
[1] https://www.zumper.com/rent-research/mountain-view-ca
[3] https://www.zumper.com/rent-research/dallas-tx
[4] https://www.indeed.com/career/software-engineer/salaries/Dal...
[5] https://smartasset.com/taxes/california-tax-calculator#vyY8q...
[6] https://smartasset.com/taxes/texas-tax-calculator#s0LEbwxtAs