Thank you so much guys for your info.
When we launched our game 20 days ago we set a few CPC campaigns (Charboost, inMobi, adinch, iAd, millenial media) spending about $500 but we didn’t see any special increase in downloads.
I have to say the game is for sure high-quality and it was built upon the success of our very similar Android game (“Ultimate BlackJack 3D”) which is very well rated and got excellent reviews.
Our new game, “Ultimate BlackJack Reloaded” for iOS is improved in every aspect and we got our first independent review which is excellent (review on appPicker).
I am telling you this because some might think the problem is in a not enough quality game.
What I have learned from CPC is that it is totally unpredictable, you can not measure the campaign success and some of my calculations shows it is even more expensive then the lowest CPI campaigns I found ($0,50).
Andrew, your results show exactly this, the lowest CPI you can get is around $0,50 (for iOS).
My conclusion for now is that I never will use any CPC campaigns, and only CPI.
But for CPI campaigns to be profitable, you have to know your user lifetime value.
If someone knows an ad network which has CPI bellow $0,50, please let us know.