I doubt the sum total of royalties for the work released by Christopher Tolkien amounts to even a single percent of those for the Hobbit and The Lord of the Rin

I doubt the sum total of royalties for the work released by Christopher Tolkien amounts to even a single percent of those for the Hobbit and The Lord of the Rings, even if you include The Silmarillion. He could just have leaned back and counted the checks incoming.