The “tell us your quietest night and we’ll get 20+ people to come that night” trick works wonders, not just for tech meetups but for things like karaoke nights and other kinds of adult social activities too. It’s a great win-win.
And if you packed their busiest night, they might make some more money but it might cause them problems and stress them out. Offer to boost their deadest night.
They all need bars to dance. They all use the same argument. And quite often they are politely asked to find somewhere else after a few months.
PS - the issue is that many social dancers want to dance over being social, and alcohol detracts from it. People have jobs and want to pay to contribute. We ended up settling on a cover charge that comes with food credit so people can booze up if desired, and buy water/snacks if not. Win-win.