According to source below, minimum ad budged for Appl'es iAd Platform is $1.000.000 in the U.S and £600.000 in the U.K. 

So unless you are a very big company and wan't to target Apple products only prices are way to high.

Source http://www.nma.co.uk/news/is-apple-pricing-itself-out-of-mobile-ads?/3020837.article via http://londoncalling.co/2010/11/will-apples-iad-fail-at-the-first-hurdle-in-the-uk/

Well, Apple made headlines again! An iPhone developer made $1,400 from adverts on his free flashlight app for iPhone 4 in it's first day! Here is the proof

It is of course no where near sustainable and novelty of iAd plays big role in this income but still  $1,400 in one day is huge money to make from adverts! I know tens of mobile web developers that would be happy with $5 income a day from their mobile site!

iAd gives %60 of  income from an advert to the developer so from a $2.00 CPC advert publisher gets $1.2. On the other side you earn between $0.01 - $0.07 per click from other mobile advertising companies such as Admob, Inmobi, Mojiva, Buzzcity, AdModa.

 As much as I am against this App hype and Apple's Walled garden approach. I can't help my self but envy!

Link to source