Me confused.
An Audible book has 2 components: 1) The Story by the Author, 2) The performance (the cast or Narrator)
Some Writers can do their own creditable performance.
Others should not even think of that (no matter how much the fans beg). For those, their share should be bigger than if a voice actor has been hired.
I won't even try and figure out which should be paid more

.
How do Movie adaptations pay?