Amazon CEO Andy Jassy recently wrote to shareholders that "Lord of The Rings: The Rings of Power is one of a number of “unique benefits” to “make Prime even better for members”. In other words, the measure of success for The Rings of Power will be in sales of Prime memberships and retail sales. 

Or, presumably, that is the case. We do not know because Amazon does not share with us the internal metrics that reflect how it defines “better”.

The same question applies to Apple - which is happy to publicize growing Services revenues but does not share subscriber numbers for subscribers to iCloud, Apple TV+, or from any other of its services. Apple's and Amazon's precedents suggest that membership is a driver of marginal revenues that doesn't require transparency with investors.

Disney’s move into a broader Amazon Prime-like membership is a response to Wall Street's new demands for higher average revenue per user (ARPU): streaming subscriber growth is now flat and now investors want to see growth in the form of more revenue per subscriber.