I've been in this situation before.
The unsubscribe process ends up taking hours of time because now you need to find 1-5 books to get before you cancel.
It's also frustrating because they won't allow you more than 5 credits, so if you have 5 credits, they will take your monthly payment and give you nothing in return.
Worse still is if you click on the wrong thing on Amazon it will re-activate your audible account automatically. I've had my audible account accidentally re-activated multiple times and not noticed (my amazon email goes to a non-primary email)
All in all I've made many payments with max credits and gotten nothing in return, purchased a ton of books that I'm only partially interested in, and actively cancelled the service at least 3 times (including being forced to waste time shopping for books to complete the task every time)
If you don't see this as a consumer trap, it's because you haven't tried to get out and stay out yet.