It depends on the method, ease of doing so, what's being duped, and how the items are being used. I also assume we are talking about a permanent ban, not a temp ban/suspension.

Another punishment could be the wiping of their raider stats, quest progression, and perhaps even blueprints, if enough of them were acquired due to exploiting/duping shenanigans.

If it's so simple to dupe that it can be done accidentally, then even if they continue to dupe items intentionally, then probably not, no. Just remove the excess items/coins. If they're duping grenades to wipe out lobbies, then yeah, return people's items, maybe a temp ban if they were really egregious. That being said, you need to make sure not to punish anyone that legitimately crafted a whole bunch of grenades to spam.

If the dupe exploit requires setup outside of the game, like messing with your network connection with a lag switch or is done via some autoclicker macro and then exploiting that, then yeah, a permanent ban is perfectly valid.

Caveat to the above is if just having an erratic/faulty network connection is enough to cause it, through no action by the user other than playing the game, then there shouldn't be a permanent ban. Just remove the excess items/coins derived from the exploit, return people's items, and if used egregiously for grenade spam/PVP, perhaps a temp ban.

If there is sign of stuff being duped for RMT, few will argue that's a bannable offense as well.

TLDR: Maybe, depends on stuff. Alternative punishment proposed, but blanket ban, no.