Not all Google AdSense ads are created equal. The advertisers for Google AdWords bid for their relevant keyword combinations, and some are much more costly than others, which is where you make your higher revenue on cost-per-click. When you place AdSense on any of your pages, the Google AdSense robot, Mediabot, will then automatically scan your web pages in order to determine the appropriate ads to be displayed on your page. There are strategies and ways to create web pages to specifically target and attract specific keywords from the AdSense program. You can create a Google Adwords account in the Google AdWords advertiser interface to more accurately determine which keywords have a higher Cost-Per-Click. You'll be able to get a feel for the average cost for each keyword. Using this new information, you may decide you wan to create a new web page or even a completely new web site.