Google doesn’t state how much they pay for each click you earn. Value for each click may range from 2 cent to $15. Highly competitive word will gain better value. Phrases like debt free, employment, make money, mp3, sex, etc. Are examples of high and competitive word searched in the web which eventually will earn you more per click. Advertisers pay more for popular terms because they are searched for more and they are more competitive. Which mean they have to pay more to attracted customer/visitor.
The amount you earn also depends largely on targeted traffic your own site. Trafic show how well the ads match your audience's interests. Higher traffic mean a lots of people interested in your blog.
Earning from adsense are also based on:
1. The placement of the ads on your pages. – the placement of add is very important. Visitor doesn’t want to annoyed with placed add.
2. Amount you receive per click.
3. Create a site on a topic you know a lot about. That way you'll have a much easier time creating a generous amount of content on that subject.