Shady book dealer Otto Jansch is described by Robert Frobisher as a "stingy Jew" (2.6.5) and a "warty old Shylock" (2.6.4), referencing the iconic character from Shakespeare's Merchant of Venice. Jansch is an opportunist, taking advantage of the desperate Frobisher in more ways than one. He tries to give him a lowball offer for a set of rare manuscripts Frobisher stole from Vyvyan Ayrs, which Frobisher rejects. Then he offers to give Frobisher a little bonus if Frobisher gives him a—shall we say—happy ending. Needing cash, Frobisher accepts that offer.
Jansch goes to show that money has power. Despite being a warty old troll, he's able to seduce, for lack of a better word, young Frobisher with the allure of wealth. Frobisher may think that money can buy happiness, but it's gone even faster than it first came.