In my experience, they offset the first 2 years of vesting with cash. So all 4 of my first years were equivalent with RSUs/Cash with the first 2 years cash heavy, and the final 2 years RSU only.
Your friends might also be including the full four-year grant in a single number, which creates a sort of nonsense figure? Another thing that increases comp is if the stock rises a lot after grant — but that would not show up in offers.
Levels.fyi is as legit as any other source, as far as I know.
It is easy the underestimate the significance of it.
Amazon offer generally gives you roughly the same "total compensation" for the first 4 years, assuming that the stock price doesn't change much.
So if they're trying to pay you 300k per year, then you get 160k salary, ~140k starting bonus each of the first two years, and ~300k of stock that mostly vests in years 3 and 4.
Their current offers are actually scaled on the assumption their stock grows 15% annually, I think.