It could be part of cut content for all we know. But Bethesda does place scams into the game. Fallout 4 had a random NPC sell you a charge card that you can "use" in Diamon City
I vaguely remember some NPCs mention it's useless, so it might be on purpose. The seller doesn't strike me as a scammer, he might be applying an actual law merchants don't care about.
Which would be the Telvanni way: isolationists and unwelcoming, but also not big on following rules.
edit: (from UESP)
there's not much reason to waste the 25 gold to purchase them. Several people will indicate as much if you ask them.
Scam, pretty sure no one cares about them in Sadrith Mora
Yeah, I know mechanically they don’t do anything. But do you think that was an accident or supposed to indicate you got scammed in universe?
It could be part of cut content for all we know. But Bethesda does place scams into the game. Fallout 4 had a random NPC sell you a charge card that you can "use" in Diamon City
https://fallout.fandom.com/wiki/Charge_card_(Fallout_4)
I vaguely remember some NPCs mention it's useless, so it might be on purpose. The seller doesn't strike me as a scammer, he might be applying an actual law merchants don't care about. Which would be the Telvanni way: isolationists and unwelcoming, but also not big on following rules.
edit: (from UESP)