Plays v Novels

I was surprised at some info I read about the publishing business recently: of 200,000 books sold last year, 190,000 sold fewer than 3,500 copies. Also, of 85,933 new books published, as many as 58,325 sold an average of just 18 copies.
My play "Dreamjobs" has sold, over about thirty or so years, about 10,000 copies.
So what does that say about writing plays and novels? Well, J.B.Priestley always maintained he made more money from writing plays than novels because they lasted longer. It's certainly true in his case for who reads his novels now yet his plays keep being performed everywhere in the world.