From Edge of Darkness Wiki
Market Sense
The Goblin Markets are notorious for trading in anything. While keeping track of currency exchange rates in the mundane world can be difficult, trying to estimate how many enamored sighs a knife that glows in the presence of child molesters is worth is just a Herculean task!
While value is a relative term, those with the Market Sense Merit can generally tell whether a certain transaction is roughly equal or not. It doesn’t force a fair deal, and a Changeling who dares to tell a hob that he’s being cheated on the basis of a “hunch” may well have social ramifications to deal with. Characters with
this Merit receive a +3 bonus to any rolls made to see through cheating in a trade or to resist any powers that would confuse or occlude the character’s perception of a deal’s fairness.