Agreed. A lot of BBSs both thrived and ruined themselves over having pay tiers. Sometimes it was pay for "premium" content which was usually warez, porn, etc. Then there was a period of charging for access to parts of the Internet (gateways), like email or usenet messages through your BBS.Other BBSs simply asked for donations and got quite a bit because people were passionate.

Ugh, modem incompatibility was an awful thing. The modem manufacturers often got greedy or out right lied about supporting standards correctly. It really was a case of needing to pay for quality. The worst period I remember was toward the end of the era with "Win modems" tied to windows. They'd pop these pieces of junk inside Dell, Packard Bell, eMachines, Compaq, and other consumer junk.

You're absolutely right about tiered access. I will say that torrent sites, especially private ones do have some levels of tiered access. As do some web forums in terms of moderation privileges. That's about the closest you get, but it's no where near as nuanced, draconian, or as powerful. The class-based access did have positive effects like you hint it such as discouraging lurking, creating exclusivity, encouraging uploads, discouraging bad actors. I kind of laughed at the web when years back they tried to do some version of that via game-ification and in most cases it ended badly excluding the obvious notables.