There's not alot you can do for $10 these days. You can barely grab lunch in lots of places.
And you're talking about a whole month where many people use it for hours every evening?
Imagine Netflix was $1 or $2 to unlock for 24 hours. I think alot of people would consider that fair. Many would pay the same to tip to someone who took 30 seconds to serve them let alone a couple of hours of entertainment.
But then that can easily escalate to $30-60 a month without batting an eyelid.
If you barely watch Netflix at all, maybe less than 5 times a month, then $10 might seem excessive. But then are those people the ones putting in the effort for a Plex server? Presumably it's not worth the effort either.