You can create 2 accounts on 1 IP with no problem, but if you create more accounts, you may have to pay a small BTC fee to be able to post articles <…>
Not really per se: Providing the IP does not have one or more unit of evil, any and all accounts created using that same IP won’t be asked to pay anything at all. When an account that uses that IP (or a neighbouring IP) gets banned, then units of evil are associated to the IP (/s).
Being so, subsequently created accounts on that IP will be asked to pay a fee that will vary depending on the number of Evil units associated to the IP. Nevertheless, providing the IP stays free of Evil units, you can keep on creating accounts on it with no issue whatsoever.
Evil units associated to IPs do decay over time, although I’m not aware of the details in terms of the subjacent algorithms used to both to assign and decay the Evil units.