You were the one that made the claim that “software doesn’t have huge ongoing costs”, which is what I said is wrong. Lots of software does, as you now agree.
Saying software does not have huge ongoing costs shows you’ve never worked on any huge software system. My works ongoing costs for hosting/scaling/storing data are millions of dollars a year.
You’re not lying, you’re just not good at networking and/or setting up Plex.
Plex does NOT charge for streaming on your own network. If it is saying that you need to pay it’s because you’ve set your network(s) or Plex up wrong.