Hello,
I am a game developer and I have yet release 3 games. I have choose to make F2P with in-app purchase.
I am a bit lucky and my game jetpack high is featured on 2 alternative store (1mobile and aptoide).
Then arround 1000+ players play it every day.
BUT, WTF! Why my ARPU is so low? Per day is near to 0.007€ 
And it is thanks to ads network, not in-app. What is so wrong in my game?
some numbers with my tracking stratedy using google analytics (a great tool that you MUST use):
For instance the 30 September
DAU: 1100
Event click on button buy something: 564 unique click (Great)
Event purchase canceled: 104
Event purchase error: 202 (serveur error …
The others purchase: 258 (maybe some have not been tracked, some cannot been purchase du to bad configuration at startup)
To implement purchase I integrated OpenIAB that allow to code one time for multiple android store. But I think there yet some bugs.
But when I test purcahse it works.
There are others devs with similar statistics? Your earning are similar?