Neat idea. I personally am put off by paying for "larger groups" but that's only because I think groups are used to having this all for free and would expect the organizer of said group to foot the bill.
Thanks - the rationale behind paying for larger groups is that it is for small businesses and creators.
One can always find larger groups on Facebook and Reddit but again it won't be of the same quality as a smaller group. What I have observed is that once the number of members in a community becomes large the content goes off-topic and moderation becomes a full time job for moderators. Also, communities tend to grow over time. Someone may not be interested in the same niche topic after few years - others who just discovered it maybe too excited. For instance what is a newcomer/stupid question for older members could be a very legit doubt for a new member. For older members these repeated newcomer questions bring down the quality of content in the community.