Jane Austen's Pride & Prejudice was published 2oo years ago – January 28, 1813 to be exact. As we learn from this Letters of Note post, Austen sold it for £110, which converted for inflation is roughly the same as selling it for £75,000 (there are various ways to calculate inflation and this one uses average earnings).  Since then over 20 million copies of the book have been sold, which works out to roughly 100,000 copies a year. That's a serious return on investment.