I guess you could try google adwords tool to estimate how much it would cost for that niche to be on top.
You can either use the adwords keyword tool https://adwords.google.com/select/KeywordToolExternal or googling with "adsense high pay keyword" to know the cost. However, i will suggest you go for niche you are good or interest than high pay niche
I try this tool for keyword research for CPC idea i select Estimated Avg. CPC. And it shows different values. For example if it is showing 0.50$ for a keyword (jalpari) then does it mean if user will click on that keyword ad i will get 0.50$ ( or something will cut down as google revenue and advertiser income) Am i doing right?
Just a guide since this is adwords cost, you get about 70% of the total if someone click. However, as i say, this is just a guide for you to compare the keyword which is more expensive
CPC is what the advertiser pays. EPC is what the publisher gets paid. "There is many a slip, twixt cup and lip". I have summarized the ways that CPC gets reduced to EPC here - http://www.vaughns-1-pagers.com/internet/top-paying-words.htm at the bottom of the page. The primary difference is here - Bids shown on the AdWords Keyword Tool are bids on the "Search Network". Bids on the "Content Network" are FAR LESS than on the "Search Network", and are NOT SHOWN. Therefore, NOBODY on the "Content Network" (publishers) gets paid 70% of what is bid on the "Search Network". In addition, only the TOP publishers get served the best ads, and only top-converting publishers get 70% of what is bid on the "Content Network" (which is typically 1/5 of what is bid on the "Search Network". For example, if I see that the Keyword Tool reports a CPC $5.00 bid, then I can expect to see an EPC of about $0.50 for me. . .