The best I've ever heard is a fraction of a cent per book, and you don't get a single cent until AFTER all the expenses have been earned back (advance, editing, promotion of the book, flying you all over the place, hotels, staff).
The standard rate from reputable publishers is 10 to 15%. It's what I've gotten from three different publishers (Hachette, No Starch, Packt). The rates for paperback, discounted books, ebooks, audio books, are all a bit different, but that's the ballpark. All these publishers also paid me advances. That’s an advance on royalties. You start getting paid more when your earned royalties exceed the advance. There is no deduction for any other expense whatsoever.
This thread is full of utter nonsense about the worlds of publishing and writing.
[Edit: minus the 15% for your agent, if you're represented by one. But as your agent also made sure you got a good contract, you probably come out ahead.]
For WHO? What publisher is offering 10%??
The best I've ever heard is a fraction of a cent per book, and you don't get a single cent until AFTER all the expenses have been earned back (advance, editing, promotion of the book, flying you all over the place, hotels, staff).