iPhone Apps - Free more lucrative than Premium?

I'm not sure whether to believe some of the figures (60% fillrates, 2.6% click through-rates, and eCPMs as high as $4.00), but I thought this report by Adwhirl could be informative to developers trying to decide on free vs. premium.

It is obvious that low fill rates equal low revenues, but I have yet to see a single ad network or optimizer that yields 100%. Oh, well, you be the judge.

Other ad networks specializing on iPhone are Admob, Medialets, PinchMedia, and even Google is planning to do so.
Adwhirl iPhone Advertising Snapshot

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