It depends a lot on the type of site you have. One of mine is commerce related, and hence when folks are searching they are getting offers via the search ads, which are appealing to them. Hence I get a decent CTR and conversion... and hence I get higher paying ads for those clicks.
You could always just ask them! If you are getting decent traffic, they might be open to negotiating a better payout. If you don't generate much traffic, you might be stuck for now until you build your site up a little more.
thank you for useful information. Especially the search box technique is a good way but i can only gain 1$ per day with 1k unique ...
Just a quick update. I placed Kontera on one of my websites yesterday and yesterday I got three clicks and my adsense stats stayed the same as usual. I know that one day is meaningless to show a trend, but my main concern is that my adsense revenue does not get affected and that I make some money from Kontera as well. And for, at least, one day my concerns were unwarranted. I will continue to monitor this and if all is positive, I will add Kontera to other sites... I will report back here in a month or so and let you know.