It's high but not unheard of (I am talking about total comp, not base salary). I know plenty of IC making that and more. Of course I am biased, since I work for an employer that does pay that kind of salary, so of course I know a lot of my colleagues. This might only be achievable if you work for one the top AI companies in the city however (Google Brain, Facebook Lab, Microsoft etc.). I don't really know how it's like outside of my bubble.

And I agree that this is not common at all but OP was talking about "top earning" friends.

However, even taking your median figure of 100k, I doubt the median salary in the bay for a senior software engineer is 300K USD (4 times more).