Earlier quoted context omitted.
Glassdoor skews heavily downwards. Even for companies I've worked at, where I knew what everyone made, its data was roughly 25-40% below reality. Also, why look at median salary? We're arguing over whether it's "possible" to become affluent as a mere employee—even if only the top 20% of engineers are capable of it, it's certainly possible.
Maybe I am a total loser, but I am not aware of any companies which "routinely" pay $300K for technical positions, not even at the Director level, in the Boston area.
As an example, I'm in the Boston area and ~2 rungs away from a "director" type title, working at a company known to not pay top dollar and without things like stock. It wouldn't take much stock for me to enter into the range that's being discussed here, albeit likely the lower side of it. OTOH none of the people I talk about this stuff with are remotely near the top end of that range when you take stock options out of the picture.