[Discussion] Duped Items loses its value?

Ok so this passed week I've seen knives with low float being posted for sale and one from I seen sold and it was #1 - 2 low fv

Does the seller have to post its duped? I feel like that person who bought it didnt no and got ripped off

but Ya seen some posts of sellers saying its really low float and only have a SS of their knifes rank on Exchange

and also if duped does it loses its value?