That seems like an unusually low salary, then. Let's pick a major public research university in the US and a department, say Physics UT Austin (feel free to play the same game with data from another public and another department, like CS at UC Berkeley). Browsing through professor salaries [1], by the time Professors hit tenure they are approaching or breaking 100K a year. Five to seven times this is 500-700K a year!
[1] http://www.texastribune.org/library/data/government-employee...