In Core, there are security permissions to hide cost rates throughout the application. You can set the desired security profile and then assign it to the relevant employees (users). Each Core screen displaying cost information offers security settings to control access to that information. For example: access to the Salary field of Employees screen can be controlled by the "Show Salary Amount" permission in the Employee section of Security > Edit Profile or Customize Profile. There is separate security "Allow Read Rate" for displaying rates on the screen. Check Core Help for details.