My $0.05 cents.
At a certain point, the developer can withdraw funds but there will be always new developers and new users buying coins, leading to the appreciation of the token.
So, we can see as a circular economy with some entry points (users and developers buying tokens) and some exit points (developers cashing out).
Comparing with other markets, App Store market represents a huge demand because there are 2 billion users using smartphone and a significant part of them (in more developed markets) buys things inside the apps.
The total amount of the transactions are $58B yearly for all app stores and is growing.