The most important thing to know is that you currently make cash purchases directly within the Audible app on iOS or Android due to app store commission policies. Instead, you must use a web browser:

: Once purchased, the title will automatically appear in your Audible app library for download and listening. The "Catch": Membership vs. Individual Purchases

Can You Buy Audible Books Without a Membership? (Everything You Need to Know)

Yes, you can absolutely buy audiobooks on Audible without a membership . While Audible is best known for its subscription model, it also operates as a standard digital bookstore where anyone with an Amazon account can purchase titles à la carte. How to Buy Audible Books Without a Subscription