Is that engineer reporting the $750,000 salary statistically significant? I feel that based on the averages excluding this salary it would be best to view that data point as an outlier.
Not in this data set of course, but if you do any kind of image processing ...
Fwiw, 250k+ seems fairly standard in some fields I've interacted with. You don't need to look very far to find them either. A good Oracle DBA will make that or more in a reasonably large corporate environment; so will a good SEO hacker in the gambling industry insofar as I've interacted with them.
It does beg one question though: how high in the corporate hierarchy were the positions with, say, $360k/year or more? If the salary is that of an IT exec in large corporations, it's not necessarily comparable to the salary of IT staff underneath them or of the consultants they might hire. (Only one thing seems reasonably sure: they weren't working for early stage start-ups.)