Some people are saying that AdSense CPC will be increased if the traffic comes from Google search with high search engine ranking of the keywords. Is it true?
No, it depends totally on what the advertisers are willing to pay per click. It has nothing to do with the page they are on.
No. CPC is cost per click and search engine ranking will only help you get more traffic. THere is no relation. But there may be higher ctr if higher search engine raking due to higher traffic.