Despite occasional complaints, in-app advertising is a validated marketing strategy: Google just bought AdMob for $750 million, remember.

In-app advertising to get users to click through to the App Store and actually download an app or game is much more problematic however.

Ad network Greystripe reckons the current cost of such customer acquisition works out at between $2.5 to $10 per download, calling it the 'dirty secret of the mobile apps advertising world'.

So, in an attempt to shake up the status quo, it's offering a new scheme.

The first 200 developers prepared to spend a minimum of $10,000 can sign up for its pay-for-download program that will cost 99c per download.

The offer is limited to free apps.

GreyStripe reckons it can guarantee this rate because its network is more efficient as it requires opt-in from users, and has higher click-through rates on iPhone due to its media-rich proprietary Flash ad format.

"Getting app downloads has become more expensive than the app development process itself," states Greystripe CEO Michael Chang. "We've heard hundreds of complaints about the current mobile advertising system and we are looking to move the needle for the App economy."

You can sign up for the GreyStripe App Download Program here.