Well, earnings from Google Adsense depends on the traffic you are getting over your site and how many users are clicking over the ad shown over your page.
why don't you try having your eyes over Google Adsense Guidelines I am sure here you are going to get all the answer in detail.
earning from the adsense only depend on the your site popularity and the number of user come to your site and click if your site most popular then you don;t need to worry about the earning its dafinatelly high
Generally there is a reason that Google bans adsense accounts. Even if the content is 100% where it should be, with perfect semantic mark up and no spam - there is a chance those sites can still have their adsense accounts banned or temporarily suspended. Generally its from my past observations that either the webmaster of that site or a vested party uses some black hat tricks to artificially boost traffic and sometimes even Adwords clicks. It might work for awhile but big daddy google will almost always find out.
Getting approved of Google Adsense to website is really difficult. Because, google adsense policies are based on traffic, unique contents, error in web page and so on. When Google Adsense got approved, you will be earning based on keywords and traffic in that page.