Sara, I’ve got a very, very rough formula for figuring out what your book has to sell to “earn out” (for readers who haven’t been through the delightful experience of looking at a publisher’s royalty statement and growling to themselves, “Why the f*ck am I not getting a royalty check again?”, earning out means selling enough copies that you start accruing royalties, also known as the Happy Happy, Joy Joy Line).
Best I can figure based on my recent experiences, you need to sell a number of books roughly equal to 40 percent of the dollars you received in your advance. So, if you got a $50,000 advance, you’d need to sell around 20,000 copies, split fairly evenly between physical and electronic copies, to earn out. I used that formula with a book I had come out back in February and it worked pretty well; I was able to anticipate the first substantial royalty payment of my 20-year career (hello, reality!) within about $500.
Just a useful bit of trivia. Thanks for your insights. Good stuff.