The difference are:
(1) We don't expect the nightclub to see us as anything more than business opportunities - we'd expect our friends to do so.
(2) If our friends ask us out to a nightclub, we all pay the cover charge, which goes to the house. However, in a paid social, the profit goes to the person issuing the invitation.
(3) If the more people, the more profit, it's unlikely that there won't be a subtle pressure on those who actually don't want/can't afford to go.
Ah, but it's really less that you *invite* your friends, and more that you notify them, just the way you notify the general public. It's clearly a business relationship
with your friends--and people do that from time to time.
It's also sort of like a potluck. We give a pass to people who clearly, statedly "organize" a potluck. As long as they're contributing too. We don't land on them for not "hosting."
This "social" is also not a hosted, invitation event.
Of course it can be done quite rudely. But I grew up in a small town, and I can absolutely see the entire community liking the idea of the social. They pay a small sum to have somewhere to go and socialize, and they get the mildly warm feeling that they're helping people a little bit, and they get to socialize w/ the couple whose wedding they know they wouldn't actually be invited to.
I can even see a community sort of resenting the couple who didn't host one of these. Bcs now there isn't a Saturday-night dance this week!