We might as well get rid of all rules then. We can't do anything about ban evasion or rule breaking. Therefore, don't ban people and let them do what they want?
Not the same thing. Account sales can easily happen outside of our control. Other rules are broken here and can be enforced here to a varying extent. Your suggestion below sounds good. There would still be plenty of private account sales:
1) Farmers and hackers and scammers would still sell (or "sell") them at a lower price than the "official" price.
2) High merit or high trust or just old accounts would still have higher value.
3) Someone who buys an "official" account may want to get some of that cost back if they decide to leave the forum.
4) I'm sure there would be all sorts of weird deals that I can't even imagine right now, like lease/share/etc.
The net effect would likely be positive though.
If we went with my suggestion of allowing people to purchase the equivalent rank in things like Silver and Gold Memberships account sales would mostly cease to happen. People only buy them for signature campaigns and half of the time the people selling them are either scammers who don't have any accounts to sell in the first place or hackers/shitposting farmers. If account sales are going to happen then let them safely buy them from the forum. It's win win. There are no negatives to this at all.