He made that much for his stories? Well, I guess JK Rowling makes a bit more, but, still . . .
I am reminded of the German writer....Karl May (1842-1912). The guy was a failed teacher who finally thrown into some debt prison and they gave him some cowboy-western novels to read. He decided that he could write that well.
So for a period of about thirty years, he wrote lots of German books over cowboys and Indians, but never having been there or talked to either a cowboy or Indian. Toward the end of his life, he made a brief trip to the US....but never got past New York state.
In some aspects, I would compare Christopher Steele to Karl May...fictional writers. Steele appears not to have been in Russia for 18 years, yet is a Russia ‘expert’.