Nine thousand members, and the team writes every answer
A company launches a Slack community, invites its whole customer list, and staffs it with two people from support who answer everything within minutes.
The response time is genuinely excellent and members say so. Nobody is being ignored, and the intent behind it is real care rather than neglect.
Because staff always answer first, members never get the chance. Member to member reply share sits near zero, so the room needs two full-time people forever and produces none of the compounding that justified building it.
Deliberately leave two questions a week unanswered by staff for a few hours. Name three members publicly as people worth asking. Report member to member share instead of total members.
Our own arithmetic on a modelled team: two people at roughly 60,000 a year each is 120,000 spent to run a channel that behaves like a helpdesk. Moving member to member share from near zero to half typically lets one of those roles move to other work, and the community keeps functioning. That is about 60,000 a year, and the room gets better rather than worse, because members answering each other is the thing people stay for.