Green’s Dictionary of Slang

to give free tickets, free board and lodging etc, usu. in the context of show business or casino hotels.

1951		US Senate Hearings on Banking 1266: [H]e came several times [...] and we ‘comped’ him [...] We do it for a number of people on the stage, on the radio, and we will continue to do it. A doctor came down, a famous doctor, a cancer expert, Dr. Max Cutler, and we ‘comped’ his room.
1961		Sat. Eve. Post 11 Nov. 21: ‘Comping’ – giving things away on a complimentary basis.
1974		in Esquire Mar. 44: The group was flown free [and] is being comped for rooms, meals and beverages at that hotel.
1986		C. Hiaasen Tourist Season (1987) 316: TV celebrities, delighted to shill for the tourist board in exchange for comped rooms at the Fontainebleau.
1992		D. Burke Street Talk 2 86: I got comped to tonight’s show.
2000		G. Pelecanos Shame the Devil 148: ‘The Black Cat’s got a good bill.’ ‘You comped?’ ‘You got it, Daddy-O.’.
2007		T. Dorsey Hurricane Punch 173: Give me half [i.e. the pills] and I’ll comp you a session.
2017		D. Winslow The Force [ebook] [C]omped seats at the Garden, the Meadowlands, Yankee Stadium and Shea, walk-into-any-restaurant-bar-or-club-in-the-city-and-get-treated-like-royalty.