If you read Boswell's Life of Johnson you'll see that Johnson himself barely scraped by. Johnson saw writing as a way of feeding himself, not of making a fortune.
And Johnson wrote many things, poems and sermons specifically, which he never made any money from but which were intended solely for the enjoyment of his circle.
I say again, no great work of literature was ever made in contemplation of profit - just in contemplation of generating enough income to write another day.
I have, of course, read Boswell. And what I read in Boswell described a professional writer constantly struggling to get paid for his labors, often unsuccessfully. His contemporary Gibbon was stuck with producing one of the great works of the English language at the behest of a patron who, thank heaven, stayed with Gibbon despite his teasing "another damned thick, square, book - always scribble, scribble, scribble, eh, Mr. Gibbon?" Would you go back to that system? We don't have many patrons these days...