5$/month for premium is fair to remove ads, Youtube has a similar but more expensive option in their app. Removing the ability to use third-party clients altogether is dumb.
From a quick google, they have 55M daily users.
How much data would the average one use, and what would that cost? What about the other costs?
How much would a not-for-profit reddit have to charge users for an ad-free experience?
Damn, imagine a stripped down donation-funded text only Reddit clone run by something like the Wikimedia foundation or Archive.org.