Depending on what kind of meet-up it is I would also be concerned about the "inverse" problem: People who would have turned up before due to guilt / moral issue

Depending on what kind of meet-up it is I would also be concerned about the "inverse" problem: People who would have turned up before due to guilt / moral issues / bad karma might now not show up because they believe the $10 is their "donation" for not showing up. Similar to late pickup fees at daycares that sometimes increasing the amount of late pickups, as rich(er) parents view that monetary penalty as a price worth paying to avoid moral blame. I think a community-wide karma/reputation system would be more powerful as suggested by someone in the comments here.