The money comes from the past few years of the stock going from 180 to 500-700, not from the severance.

E5s making $900k, $E6s making 1.5m… quite common.

That might happen for a year or two but it's not like they're getting refreshers priced at 180. After paying all the taxes, and factoring in the HCoL area they probably live in, I doubt many people are retiring early on that. Very few high earning people would quit their high paying job so they could live a "normal" life and worry about bills and expenditures.