On the reserve its $75 to become an AU or you can become AU on amex platinum
$175 per year for the first three authorized users on amex platinum.
Do Amex Platinum authorized users get priority pass?
They get most of the same benefits as primary cardmembers, minus the airline fee credits and Uber credits. Adding three authorized users for under $60 each and getting them Amex Centurion Lounge access, Delta SkyClub access, and a Priority Pass membership, among other benefits, is pretty darn good.