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.

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.