We were overpaying royalties. Contrary to the ideas in this thread, I think most of the people working at Amazon really do believe in earning customer trust and customer obsession. I never experienced anything even remotely like someone saying "We could earn a bit more by cheating!" And if I had, I would have felt complete confidence in raising a red flag to literally anyone above me in the org chart (though, of course, I would've gone in order). Conversely, I did experience many, many genuine people expressing earnest opinions about what they thought was best for the customer.

I would not be surprised to learn that there are harsh or exploitative terms for audiobook publishers. In that sense I think Amazon would consider that serving the customer means securing better prices. I would not be surprised to learn that some element of the people responsible for getting this working correctly were not doing so in some way (either because they didn't understand, bugs in the system, or they were too busy doing other stuff). I would be really surprised if they were intentionally cheating Audible publishers out of relatively small sums of money though.