I don't think it's about the money. SC has tons of that. It's about keeping things simple. SC is a relatively small company without that many employees and they want to keep it that way.
From their webpage:
http://www.supercell.net/about
While games are certainly big business, we’ve found the best way to get big is by being small. Small teams, that is. Need proof? Clash of Clans and Hay Day were created by teams of only half a dozen developers each. There's no clumsy hierarchy or bureaucracy here, just exceptionally talented [super nice] people with absolute freedom to pursue their creative vision.
Our small philosophy is at the very heart and soul of Supercell. To make it all work, there are three simple yet essential ingredients: insanely talented and creative people, unrestricted freedom, and great team chemistry. It’s a potent mix.

