I think that Making money is part of the undergoing plot which is represented by the idea that Vetinari has about making huge renovations in the city using the ''Device'' found in THUD. In fact Vetinari needs stable and running economy and that is the reason why he appointed Moist as chairman of the bank- to revive the financial situation in the city.
As to the funny part- it was outstanding idea to introduce the idea of the ''funny games'' that people play in the bedroom which resulted in Mr. Fusspot obtaining his new toy