Grab It Magazine:
"We’ve all had an inkling for some time now that in-app purchases (IAPs) are a ludicrous source of revenue for developers. The proverbial pot of gold, if you will. After an in-depth look at the financial reports of casual game developer King (of Candy Crush fame,) there is certainly no doubt left. Since 2012, King has raked in over $4 billion in revenue from IAPs across all its titles. I don’t quite have the vocabulary to express how unfathomably large that number is."