Snowy
Explorer
not that its that relevant to whether I would allow it or not but....
in the case of the repercussions, no trader worth their salt is going to admit publicly that someone made them a laughing stock by selling them fools gold, it'd encourage every young trickster to come and have a try wasting their time and probably some experienced scam artists to come and knock off his place of business in a more complete manner (if he made that simple a mistake he wont have done xxx, where xxx is a security precaution).
depending on power level of you and the merchant I can see a whole host of possibilities
being more careful in the future, not trading with you again, jacking up prices, selling dodgy goods to you, acquiring objects you want and holding them in a monopoly, bad mouthing your name to other merchants, trying to frame you for bad trade/a crime, having your stuff stolen then selling it back to you, having your stuff stolen, hiring a bounty hunter, hiring an assassin, hiring an adventuring party to make the money back from you, dealing with fiends to get them to assassinate you, arranging to have your base destroyed, arranging an invasion of your home neighbourhood by black dragons, getting the unlimited hordes of fiends/devils/githyanki/mindflayers to invade your home prime material plane and enslave all your race and kind.
someday I shall run a thieves game and have well statted merchants and a good developed city and let the players run riot and see what I can build from them sowing the seeds of their destruction!
in the case of the repercussions, no trader worth their salt is going to admit publicly that someone made them a laughing stock by selling them fools gold, it'd encourage every young trickster to come and have a try wasting their time and probably some experienced scam artists to come and knock off his place of business in a more complete manner (if he made that simple a mistake he wont have done xxx, where xxx is a security precaution).
depending on power level of you and the merchant I can see a whole host of possibilities
being more careful in the future, not trading with you again, jacking up prices, selling dodgy goods to you, acquiring objects you want and holding them in a monopoly, bad mouthing your name to other merchants, trying to frame you for bad trade/a crime, having your stuff stolen then selling it back to you, having your stuff stolen, hiring a bounty hunter, hiring an assassin, hiring an adventuring party to make the money back from you, dealing with fiends to get them to assassinate you, arranging to have your base destroyed, arranging an invasion of your home neighbourhood by black dragons, getting the unlimited hordes of fiends/devils/githyanki/mindflayers to invade your home prime material plane and enslave all your race and kind.
someday I shall run a thieves game and have well statted merchants and a good developed city and let the players run riot and see what I can build from them sowing the seeds of their destruction!