Kasch is running a very popular tooth and wig shop in the Diamond Quarter. He also appears to have good knowledge on the laws of Orzammar which he uses to take advantage of the Casteless. It is also known that he is married.
When he notices that the Dwarf Commoner has all of his/her teeth, he offers him to buy 1 for two teeth. The Dwarf Commoner can threaten him either by using violence or by revealing for whom he is working for, to which Leske intervenes and ends the discussion.
However, if the Dwarf Commoner picks a more diplomatic way, he will raise his offer to 150 which is his final, as he says, as he can find other casteless to buy theirs with much less money. The Dwarf Commoner can then ask him if he has a legitimate work to which he replies with a legal answer that it was decided during the reign of King Darbir that it insults the Ancestors for casteless dwarves to perform any work the recognized lineages can do.