Graham to Americans: If bill isn’t passed in 48-hrs cut off Congress’ pay
https://www.youtube.com/watch?v=1Eskj4l3hRc
So, to return to the original question: Who decides how much to pay Members of Congress? The Members decide a level for compensation, the President signs off on the salary laws they pass, and the public may express its approval or disapproval in any way that is lawful—especially at the ballot box. Skepticism of the Members’ power to determine their own salaries is warranted, but there are legal and, as history has shown, political constraints on this power. As with almost everything else, Members can do only as much as the public allows.
https://www.congressionalinstitute.org/2019/02/26/who-decides-how-much-congress-gets-paid/