I really, really think we need to move away from using the term "purchase" with these sorts of things. You are not buying the title, you are buying access to the title so long as the title rights owner feels like you should have access to the title.

Amazon isn't alone, Valve/Steam has a similar issue, all music services, eBook platforms, audio books, etc. I think the war has already been lost on that front... you do not own anything and that's not going to change unfortunately.

For me, describing this as a "lease", perhaps with an explicit renewal date (that may or may not be free maybe) would make a lot more sense.

For Example:

    Lease "Final Space" for 10 years (Renewal Date: 9/28/2032): $29.99

Or:

    Lease "Final Space" until 12/31/2022 (Non-Renewable): *Reduced Rate* $7.43

This would give platforms a predictable end-date, and the possibility to charge a reduced amount as the title's contract expiration date nears... plus charge a reduced fee for "renewing" a lease (and giving them future revenues on the same titles).