Smells like you are being scammed or whatever. Don't pay shit to anyone if asked.
No, that is no scam. That is when you register a new account on bitcointalk and you use an ip that was previously banned. That only should ensure that a scammer or spammer isn't simply creating the next account and starts over.
With the fee it costs a bit and might make it not worth anymore to scam or spam.
Scams aren't moderated here, so scammers aren't banned (unless they're breaking forum rules, but more often than not they don't break the rules of the forum).
If my understanding is correct, the fee is in place to prevent spammers and trolls to come back to the forum and continue breaking rules. To do so, they'd have to send a little bitcoin to the website, and that wouldn't be worth the time of some who've been banned. Like BadBear said though, it's better than a full IP ban, especially if you decide to use the website over Tor or a public VPN.
But the bad karma is all about IP's that was used by banned or even nuked users. The ip's they used will get bad karma and everyone trying to register with such an ip will have to pay for using it. That way it will get expensive to scam or spam.
And yes, there are accounts nuked not seldom. Which means the account including all posts will be killed.