I dunno about that. Plex has lots of market share and plenty of “well I bought the pass when it was $60/$90” people aren’t gonna be personally affected by them locking more and more functionality behind the pass. So they’ll keep using it and recommending it and talking about it, and the centralized account management stuff (which Jellyfin won’t copy, because not having that is the point of selfhosting) will always be more convenient than setting up VPNs or other tools like external auth for Jellyfin sharing over the internet.
Discourse about this everywhere always boils down to the same comment: “I bought the plex pass and honestly I’d do it again for $300 just to not deal with handling my own authentication system, plex remote play Just Works”. Or something like “I refuse to use a $20 HDMI android TV box instead of my ad-ridden smart TV or PlayStation 5, and those don’t have apps for JF”. These guys are literally in this thread, on Lemmy, the Reddit for people so FOSS-friendly they use Lemmy instead of Reddit.
Server costs? Plex’s serverside only handles auth and verification. Once the client connects to the server, any media is sent peer to peer. There’s no stage where the video goes “to plex” or “from plex”. Saying plex needs to charge a sub fee to make up for bandwidth is like saying qbittorrent should do the same.
Unless you’re talking about the content Plex serves, the ones you have to walk every user of your Plex server through deleting from their apps’ homepage.