I don't think that's quite the way to look at it. Insurance is for
disasters. Unexpected
costs should be covered by a reserve fund - so, in effect, you self-insure for that kind of thing.
Neither of us know anything about the financials of this group, but I can imagine a scenario in which they catch on, and their userbase scales 47x overnight (I mean, they're hoping for that, right?) and they need to spin up new resources right now. Good luck getting someone to write a "we got really popular" insurance policy, let alone pay out within the matter of hours / days they'd need the money. The "extra", right now, could be going towards filling up their reserve fund. Or not - we don't know - but that would be one of any number of legit reasons for asking for more than marginal-cost contributions.
Anyway, people supporting this aren't doing it out of an entirely economic cost / benefit calculation. They believe in whatever mission the org has, and have a high-trust relationship with it, so "paying" more for whatever "product" won't be a concern for them (at least right now). The contribution model the organization has chosen is ideally suited for that sort of (not purely business) relationship.
This group likewise doesn't interest me, but I can tell you stories about organizations I've belonged to and / or helped run that have worked that way more successfully than they would have in any other.