hack the google db and find out that which advertisers are paying most.and only allow those advertisers in your site.there is no exact figures but only estimates available on net,unless you do what i suggested earlier
You should stop going for high paying keywords and go for lower paying keywords but where you can get more trafic easily (less competitive in terms of SEO).
don't worry about the highest paying keyword, you're less likely to make money. focus on getting clicks, not on the keyword itself. yugo,