(The dichotomy between "I must earn a gazillion dollars because I'm a senior dev" and "I will not pay money (that pays those salaries) for software" that's so prevalent on HN is mind boggling)
- development costs money
- workplaces cost money
- people want to eat
You can pay for Plex with money (Plex Pass). And while I sort of dislike them pushing their own content and monetization, it can be easily switched off in settings.
As long as they have something to keep them above poverty line: https://staltz.com/software-below-the-poverty-line.html (among other articles, the question of how free open source isn't sustainable is discussed often)