Wow, 19 comments and not one of them questioning how the person knows their salary is 3 times their peers ? Isn't it obvious that anything that can be said about the HR's actions can also be said about the manner in which the person themselves got the information to make the comparison ? Why is this even a legal issue ? overreaction, much ?
Maybe OP hired/interviewed others teammates. In my experience in small teams, when I've interviewed candidates, I knew the salary range for that position.
salary ranges are commonly posted on job listings on AngelList, etc. so he could of saw it there when they were hiring for the position or if they are currently hiring for that position
also glassdoor posts salaries of different positions at companies so he could of saw it there