some guy who have been there explained it for our newspapers. they rent a club, they hire few pornstars who are doing sex at the parties, the rest of the girls are students and so, paid about 1000czk/50usd, for each party, and they get drunk for free there, so some of them want to fuck and will fuck. if the girl want to go to next party, she have to take two new girls with her
thats what the guy said