Certainly.

Whether or not an account is sold or not has to actually matter to a site in its behavior / outcome. Otherwise it is just another account without a grievance and for the sake of argument, a legit or traded account would be functionally identical. If they don't misbehave, they're just another account. If it misbehaves, it has to do so visibly. Bad ratio, offensive posts, etc. Since this however is visible and flagged regardless of whether an account was sold or is just someone who is a bad apple, it does not matter. In turn, neither does the underlying IP matter.

What matters is whether the account misbehaves.

Since this can be policed regardless of who is behind it, or what IP it has, the argument that you need the "real" IP is moot, and doubly so, since normal home users have dynamic IP addresses to begin with and anyone in their area gets allocated IPs from the same connection pool.

Overall, the policing as a site admin has to be done, whether its overlooking real or traded/bought accounts. You can argue that there might be more work if VPNs are allowed, but given that I know a dozen sites that do just fine while allowing them, it does not appear to be an issue that either prevents site moderation nor does it impede site operation, so it is a questionable and hard to prove argument in terms of how big an impact it has to begin with.

The trading and selling of accounts itself in general apparently isn't dead just because some sites forbid the use of VPNs, so the argument that it prevents the trading in and of itself is questionable, too. Easier or harder, if someone is out do do stupid crap, they'll find a way, regardless of how the rules are formulated.

However any and all kinds of accounts regardless of VPN rules remain moderated and policeable, so the argument against VPNs is hollow.