How much money can I expect? What is the eCPM?

The CPM of the interstitial is very high (> $2), However, you can show an interstitial ad less often than you can show banner ads. All in all, the AppLift interstitial significantly outperform competing offerwalls, app wall or smartwall in terms of overall revenue per app install.
The AppLift banners provide leading eCPMs, depending on your audience the CPM may be between $0.50 and $1.50.