One thing that skews these numbers is what counts towards the denominator. Facebook has tons of contractors working inside their datacenters doing breakfix. Do they count towards the 'employee' count?
The other bit is how much of SV's employees are paid in stocks; after 4 years of RSU granting cycles and appreciation, you may well be earning more in stock vests than base salary.
The other bit is how much of SV's employees are paid in stocks; after 4 years of RSU granting cycles and appreciation, you may well be earning more in stock vests than base salary.