Experienced users know, that if they want the best, in many cases, they have to pay.
Agree 100%. But I see a very simple UI for that: the free directory checked by default, plus you can check/uncheck “Freemium” and “Paid” checkmarks, so it is your choice where to search a plugin: in one directory or all of them. Very simple, very intuitive, both for users and developers.
For more convenience, there can be subdirectories “One-time payments” and “Subscriptions” in “Freemium” and “Paid”, because many users have no problem of one-time payment, but are cautious with subscriptions.