Mr Universe is betraying the crew by luring them to their deaths. Apparently in return for money ("coin")
The operative removed the sword from his briefcase even as Mr. Universe turned his chair around toward him. "There. Toss me my thirty coin, but I got a newswave for you, friend—"
Whatever information this man wished to impart was lost as the operative ran him through. Mr. Universe seemed surprised, as if he could have all this information at his disposal, yet be wholly unaware of the usual fate of traitors.
Serenity: Official Novelisation
The traditional (biblical) payment for being a traitor is 30 pieces of silver.
And said unto them, What will ye give me, and I will deliver him unto you? And they covenanted with [Judas] for thirty pieces of silver.
Matthew 26:15