I'm not sure freemium games with in-app purchases are a very good model for apps in general (I'm not saying you're suggesting anything other than that they make a lot of money, just pointing it out in the context of this discussion).
It's hard for me to see how they're anything but a form of unregulated (yet) gambling/exploitation of people vulnerable to gambling.
Who in their right minds think that tens, hundreds of dollars is a good price to pay for virtual gemstones?
At any rate, for others that where unfamiliar with Supercell, I'm assuming parent means the makers of:
