The tactic was highly successful on SA, but it can only do so much. Having a cover charge keeps out lazy spammers, children, and casual vandals/trolls pretty well. Unfortunately, it doesn't do anything to keep out those who are determined to be disruptive and have anything resembling real income. Even with 5 bans a month, $50 is trivial to any adult with a job if they really, really want to stay and cause havoc.