Professor Cowen has offered this link at Marginal Revolution:
http://www.avclub.com/articles/neal-pollack-on-rebounding-from-massive-hype-and-s,93689/
--which illustrates that the pendulum continues to swing between 1735 and 1776:
Swift to Wm. Pulteney, 12 May 1735: "I never got a farthing by any thing I writ, except one about eight years ago . . ."
Johnson in Boswell's LIFE (vol. III), 5 Apr 1776: "No man but a blockhead ever wrote except for money."
But the Pollack interview is its own inspirational and cautionary tale and worth a look. (Don't know him or his work otherwise, though, first I've heard of AVClub, too.)
Verrrry interesting. That whole AVC site is also interesting.