What does an author earn per book?

People are always curious about this, so I thought I’d post it and refer to my previous post about what kind of sales numbers it takes to make a living as a fiction author in the US. Of course, the royalty rates depend on what’s in your contract. Many contracts have sales volume break points. For example, an 8% royalty on the first 50,000 paperbacks sold, 10% on anything above that. But this should give you a good feel.