I would like to chip in here.
We have "Adsense for Search" on our site which are local directories. We have this on our search result pages and we can pass on custom values to google adsense code.
Our CTR for "Adsense for Search" is almost 3-4 times (sometimes even more) of CTR of our normal "Adsense Ads".
Also our Revenue is more than 2-3 times for "Adsense for Search" than "Normal Adsense Ads".
So all in all what we can understand from our sites that "Adsense for Search" gives us much better results in terms of CTR and Revenue than normal "Adsense Ads" on our site.
So I would like to support an argument here that Google SERPs must be getting much better results in terms of clicks and revenue than to clicks and revenues on Adsense Publishers Site.
But again ofcourse not every site is Search based and most of the sites are having articles or different sort of information and cant show "Adsense for Search" ads on their site.
And No we are not premium publisher with millions of views. Google approached us for showing "Adsense for Search" ads on our site and we acceepted to show them on our Search Pages.