My question is what is the best ways to put this to an end. Because from his profile I sees lot of tags.
The only way to stop this is if theymos decide that selling accounts are against forum rules but since that is unlikely to happen, nothing can be done really other than tagging them. After all, this is not the first time we see offers like that, with the only difference that they are rarely posted in meta.
And yeah, account prices are set so low on purpose to lure gullible ones thinking they can get accounts that cheap.
This is exactly my thought, unless selling of account is forbidden, things like this will not stop. By the forum rules, the person selling the accounts did not violate any rule but the action unethical. I think it's high time Theymos review the account selling policy because stopping that will discourage people who hack accounts for sell from doing that.