Yeah, I considered including at least the Simarillion in the calculations, but the sales numbers for LoTR and the Hobbit are so staggeringly large that including his other works seemed pointless.

You raise a very good point about holding him responsible for all the works he inspired through. He invented a whole new sub-genre of fantasy, leading to hundreds of millions (if not billions) more books being printed.

And think of the movies! I wonder how many trees died to print scripts and build sets for 6 movies and a TV series