Is it permissible to sell an item which is not authentic (i.e. real) but the people know the item is not authentic?
Shaikh Salih al-Fawzan hafidhuhallah:
He says oh Virtuous Shaikh (may Allah facilitate for you), ‘what is the ruling on buying and selling imitation goods like watches, pens, and other than that?’
“You notify regarding it. There is no preventative for you to sell it or buy it. However, inform that it is an imitation and not an original and that its price is cheaper than the price of the origin. As for those who cheat the people and sell it as if it is an original and take the price of the original while it is an imitation, then this is cheating when [it is known that] the Prophet (ﷺ) said:
من غشنا فليس منا
Whoever cheats us is not one of us
If the buyer does not know, then clarify to him and so he sees it as an imitation. So he does not take it thinking it was an original and pays a high price and [the seller] exploits his [the buyer’s] ignorance. This is not allowed. This is cheating”.
[Tafseer Surah al-Hujaraat no. 68 starting at the 50 min found here]
Faisal Ibn Abdul Qaadir Ibn Hassan