Nathan
this is about Android only:
ok, I was too harsh for AdMob. Avg eCPM (for mine apps and friend apps) is 1-2$ eCPM, and this network provides best fillrates (because it's Google); anyway in worst case: 0,36 eCPM, in best case 3,55$
The other issues (in case of banners ads) are:
- placement on banner matters (bottom gives huge boost over top; at least in case of portrait layout and mobiles)
- clickability of app (more clicks user do in app = the more clicks on banner you get too)
- type of app (kids make more clicks than adults).
In case of Java apps my friend usually get 3-6$ eCPM for appwalls, interstitials etc. and of course additionally $ from normal AdMob banners.