The publisher Metropolitan Books looks like it's part of Macmillan so they're likely a traditional publisher, which suggests he got a pretty healthy advance on

The publisher Metropolitan Books looks like it's part of Macmillan so they're likely a traditional publisher, which suggests he got a pretty healthy advance on the book because of his fame. I would also guess that even if he sold enough books to earn out the advance, his take on each incremental book is really small as the publisher took most of the financial risk with the advance itself.