All of the sites I have running adsense aren't really targetted for ads, but rather selling DVD's and Merchandise (the adsense is just a bonus). That being said, my highest single click from adsense was $1.76 Still enough to make me happy!
When I ran kromefx.com i averaged very low, but there was one day I had a click that was worth $10. At the time I was only making about $20 per day on all the clicks so that was highly unusual.