Why do we pay to go to parties? (Geneva)

When I lived in London, I used to organise parties. Normally when I rang a bar and said I was going to bring Protected content educated and mostly wealthy people to their bar and fill it for a night, they would fall over themselves to offer free DJ, special prices on drinks, free food...even often free drinks.
So I wonder why we have to pay here to enrich a bar owner, and where our entrance money actually goes.
Either the organisers , and fair play, they seem to do it for free, are not very good at marketing, or there is something else going on.
What do you think?