There's a huge international market of potential app users that tolerate ads but would never pay to purchase an app. Even in affluent areas, many people balk at

There's a huge international market of potential app users that tolerate ads but would never pay to purchase an app. Even in affluent areas, many people balk at a $0.99 app but are totally fine with ads. This, of course, is the entire business model of Facebook, Instagram, etc. The billion dollar question is: how do you monetize non-paying users, at scale, without ads?