> Pretty sure a top cryptographer or security expert should be worth several times that [~150K x several times]

On the other hand, I often wonder whether folks who are pulling in nearly a half million dollars in compensation in the private sector (as individual contributors) are really worth that much or if they're just benefiting from a relatively temporary windfall caused by scarcity in tech talent.

Keep in mind that government salaries still do come with decently good benefits and vastly more job security than start-ups. That is attractive to lots of people especially late in their careers. Cutting edge IT-related positions aside, non-cutting edge jobs in government do not face such stark competition with the private sector.