"What do you mean that she didn't ask for payment?," Zhen Jin asked, "making documents ain't cheap, let along forging them. She must have asked for something."
As the Zhen Clan's resident torture master, Zhen Jin had familiarized himself with a lot of the...unsavory elements of society.
Not necessarily because he had a vested interest in such things or looked at it as a hobby, he did so because many of the people he had to extract information from tended to be of the criminal variety.
Many a scoundrel had attempted in the past to use forged documents and the like to try and extort the clan for money, rare aether beast components and other such things.
Sometimes it worked, sometimes they got caught and that is when Zhen Jin started to pick up the tricks of the trade...and just how expensive it was to do so.
Therefore, when Zhen Jin questioned the circumstances of a deal, the brothers listened.