Great way to guarantee I won't attend your meetup

Well yes, but 100% attendance of zero people is still zero people.

If you distributed the $19 to the people who did actually show up... you would actually get people to show up... maybe there's some kind of business plan embedded in your comment.

That is a fascinating idea that I'm surprised I haven't heard before. I guess implicitly it sort of happens when the money is spent on food or drinks.

Double-digit is too high, you'd have people showing up just to get paid - which is not what you want.

There might be a sweet spot around $3-5 for that model.

Even better: charge $5 to book; attendants will be refunded the fee; any leftovers will be used for refreshments at future events.