I co-organize a handful of Meetup groups, and we already pay a non-negligible annual fee. There's definitely money to be made.
Most people seem happy shelling out $100-200 per year for a membership. $2 per attendee per event is simply exorbitant, noone will be able to afford that.
It's so bizarrely extreme, I can only assume it's a psychological "anchoring" tactic - a patently ludicrous number that makes the "real" offer (2-3x fee hike) more "reasonable".