The actual adsense CPC compared to the GKT approximate CPC

We all know that we shouldn't expect our adsense CPC to be as the one suggested by the google keyword tool CPC, since it's the average of what advertisers pay to be displayed on google's network itself. And generally they pay lower for the display network (adsense sites)

But how much lower we could expect? That's critical when researching new niches. I pulled 6 of my sites and estimated what % is the actual adsense CPC from the GKT approximate CPC.
(All of those has got few hundred clicks, on which i've taken the average CPC)

the first column is the actual CPC i get on average
the second is what GKT suggests
the 3rd is how many % is the actual click from the suggested click
0.22 0.45 48%
0.15 0.15 100%
0.47 2.1 22%
0.60 0.93 64%
0.31 0.49 63%
0.32 1.05 30%

54% is the average % for all the above 6, but as you can see for particular keyword it fluctuates between 22% and 100%
That's huge and means you can't predict even close how much you would make.

So i would appreciate some more data, if you want to do the same for bunch of your sites and report here, we will get better idea how much we could expect from a potential keyword.