Im a little bewildered too by the C2-Admob partnership. I have made apps in C2 using the Admob interstitial plugin and it generates way, way, less than a similar app written in Java (Android) and coding in the Admob key reference.
There seems to be a definite pattern between impressions reported and low revenue using C2.
Below is a daily report for some of my apps. The highlighted, yellow, app is the only C2 app, all the rest were created using java/Eclipse.
Its as if the impression is fetched but never displayed. The ads do show so Im not sure why this pattern exists in all my C2 apps.
Just throwing in my 2c.
PS - If you're using banner ads, its historically very low when compared to interstitial. But 5c is way too low.