Every click >1.50$, but low impressions!?

I set up a new site recently on a specific niche topic, which starts to attract some visitors now, after promoting it a little bit and some link-building.
The past days I got a few clicks at the site, each between 1.50$ an 2$ worth, which I think is not bad!
The only strange thing is that there is such a difference between the number of ad impressions shown at the adsense channel and the number I would expect checking the webstats (visitors/page impressions) of the domain.
I see only about 1/5th of ad impressions I would expect taking into account the number of visitors at the site.
Can anyone tell me what the reason could be?
There should be enough ads on the topic, I checked that with the preview tool.

 

Do you have adsense on every page of the site?

 

I get that sometimes when just public service ads show up.

 

Yes, on every page except contact/disclaimer/links page

 

Is there a way I could check or get proof if a significant number of public service ads shows up?

 

Check to see what browser your visitors use. If they use Firefox with adblock or have javascript disabled then they will not see any ads.