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.
More importantly it's nothing to billion dollar corporations or governments. Money should not equal speech. Instead I think that firstly we need a "proof of personhood", a way to identify real individual users and distinguish them from bots and shills that run multiple accounts. As it is now the system can be easily gamed which works great for those who have plenty of resources. Genuine users get the short end of the stick.