Isaac Asimov was known for being a prolific writer. He wrote more than 400 books.
In July 1959, he had a lunch with one of his editors, who advised him, “…not to write so busily. He said my books would compete with each other…” The economist’s law of diminishing returns says that producing ten times the quantity does not yield ten times the return. Here’s how Asimov responded:
I was rather glum that meal and gave the matter much thought afterward.
What I decided was that I wasn’t writing ten times as many books in order to get ten times the monetary returns, but in order to have ten times the pleasure. As far as pleasure was concerned, I had not yet reached the stage of diminishing returns—so I continued to write as quickly and as copiously as ever.
Source: Asimov, Isaac. In Joy Still Felt: The Autobiography of Isaac Asimov, 1954–1978. Doubleday, 1980, page 165.