Hi! I highly recommend you consider looking into a Kindle Unlimited (KU) subscription (currently they are running 2 months free if you aren't subscribed). I know that sounds strange because you want audio books, but here's why I recommend trying it out: even if you aren't actually reading the Kindle book, there's a large supply of titles on KU that have Audible "add on" narration included for free (here's Dracula as an example) when you borrow the book. When you borrow the book + audiobook add on, the title will appear in your Audible library/app as if you purchased it.
Secondly: if you borrow a book in KU that does not already include the Audible "add on" for free, the borrowed book is seen as "owned" by you on Amazon and will be able to purchase the Audible Add-on (usually) at a highly reduced rate-- such as $1.99. (here's Scarlet Odyssey as an example).
KU is truly unlimited-- you can borrow 10 titles at a time and return/re-borrow as much as you want. Its true that the majority of the titles are self-published, but there are plenty of excellent titles including a rotating set of titles from major publishers. I typically sub to KU for 2-3 month intervals and then wait for a list of stuff to pile up that I want to read/listen to before re-subbing.
I have about 100 titles in my Audible library, but I have only actually bought/used about 20 credits. The rest of the titles I got through Kindle add-ons over the last several months.