Been going on for a while:

High-Tech Employee Antitrust Litigation is a 2010 United States Department of Justice (DOJ) antitrust action and a 2013 civil class action against several Silicon Valley companies for alleged "no cold call" agreements which restrained the recruitment of high-tech employees.

<https://en.wikipedia.org/wiki/High-Tech_Employee_Antitrust_L...>

Using a rent estimate would be a brilliant way to double-check if you are overpaying salaries. /s