'No, I didn't come all this way for nothing; the attendance at your club is not my problem'
It is if you want a rebooking! performers do have some impact-their own websites (kept up to date and accurate) their own mailing lists. To assume that any poor attendance is the resposibility of the club is somewhat unreasonable. In the current financial situation, surely it is up to everyone who is involved's responsibility to do what is required to maximise audiences.
On a practical note - if Kosmo is booking anyone direct or thru' an agent - get a contract even an email confirmation is better than nothing- handshakes are for afterwards. Get it in writing. If it's a basic fee or a fee against a door % Make sure that you have the minimum amount available before the evening starts (personally I wouldn't pay before the end!)- don't assume that the door take will make up any shortfall in your accounting, because that's the day that only one person will arrive!!
By the way, have you seen your psychiatrist recently LOL
good luck
chris