I used to work in the industry. At least when it comes to fiction, it has always been hard to make a living as an author. A very large number of first-time auth

I used to work in the industry. At least when it comes to fiction, it has always been hard to make a living as an author. A very large number of first-time authors never earn out their advance and therefore aren't able to get another book published. A reasonable portion of a publisher's authors are "mid-list", which consistently turn out books that earn out the advance plus a decent amount on top, and each new book also gives a slight boost to that author's back catalog. Long-term, this is how the average author earns a decent living: Output is maybe 3 books every two years. Early on, the advance might only be $15k to $30k per book, though once they earn out the advance they begin getting royalties. Once they have 6-8 books published, they have an audience and enough of a back catalog that they may earn up to $50k/book with royalties from the back catalog adding on a healthy bit on top. However "mid-list" encompasses a wide range, so this can also be lower or higher, especially because a mid-list author with 20+ books, turning out 3 books every two years, may still only get $40k advances based on new book sales, but with so many books in their back catalog even selling only 1000 copies of each book each year can add another $30k on their annual earnings. More if they're popular enough to get audiobook deals as well. These are the authors that basically keep the lights on for the publisher. Overall though, profitable publishing is a business of breakout hits, the authors that sell 50,000+ copies and hit the best seller lists. Failed first-time authors and mid-list authors may mostly cancel each other out on profit, and it's those few hits that push publishers into the black.