YouTubers don’t build their communities on YouTube they build an audience which they then concert to communities on sites like skool, discord etc. 

There they build different incentives to people to join - masterminds - workshops whatever. This is where the value for their viewers lie and why they are okay with paying so much. The ytber provides free value on yt and then really juicy value lies in the communities. 

Ad revs aren’t even the big driver of all of this.