The majority was from stock and significantly boosted by the rising price. If I stayed it would have decreased slightly over time due to the stock price levelling out.
If you achieved steady career progression at Facebook over the last four years (reach E5 level, a couple of promos) and not get fired them making 400k+ would be common. I’d hazard a guess that probably 50% of new hires achieve this. Base salary would be 200k and the rising stock price makes up the rest.
For what it’s worth I left the Bay Area and Facebook and cut my compensation by more than half to do so.
With stock compensation it's pretty easy because of the appreciation of company stocks. 5 years ago, Facebook was trading at $24/share. It now trades at $193/share, a roughly 8x increase. If your compensation package included $125K/year in RSUs - something eminently achievable even with just a few years of work experience - you're now making over a million a year as those stock grants vest.
This discussion thread seems to be a mix of both, so...YMMV.