to who do you mean one would pay a small charge?
The forum itself. I personally haven't experienced it, but it's probably quite procedurally similar to paying for a Copper Membership:
Q: Why is my IP banned? What are those units of evil?
A: Your IP might be banned because it was used by a user that got perma banned. Don't worry - IP bans decay over time if there's not too many of them during a small period. If you register using a banned IP, are using TOR, VPNs or well known proxies, you will have to pay a small fee. This is to prevent spammers while allowing legitimate members to post without many restrictions.