I'd be happy to pay $5 a month to a site that essentially "hosts subreddits" for niche communities.

I think a lot of other people would, as well.

I could spin up a bulletin board on a $5 VPS for a few thousand of my closest internet friends easily enough, but there's something to be gained from a single, well-known site with a well-designed interface (not reddit!), a large existing userbase, and useful discovery tools.

I should probably stand up a lemmy instance.