There's a FAQ posted here that answers these questions. forums.digitalpoint.com/showthread.php?t=23238 Follow the link "Adsense FAQ" and then look for the question "What are highest paying keywords?" I dont know if i can directly link to it. still getting use to the rules here ^^;;
I think highest paying keywords will be insurance, law related, etc. However, it also changes. Mortgage used to be high paying keyword, I don't know what is the situation now. Also it depends on if the advertiser wants to put their ad in your web site. No advertiser wants to put ad in a made for adsense website for a random click that will pay the site owner $10. If it is a reputable site and advertisers compete for adplacement in the site, the click rate will go up.
Be careful. Google automatically flags sites that pop up in the highest paying niches (ex. mesothelioma), in which case you could be wasint a hella lotta time.
Based on my experience high paid keywords pays lower per click. I'm earning more per click on low paid keywords
Man, forget those high paying keywords... Work on a small niche that will bring not only high paying keywords but also good traffic and good earnings. If you take care of a small niche, it will take care of you