Some times, you will see low earnings per click, where some times, you will see good earnings. It also depends on your site's Niche. Adsense earning per click isn't constant.
seems like they are taking more from advertisers and sharing less with publishers.Effectively increase in google profit.
Gotta make money where you can. Google never promised you would receive huge payouts for displaying your ads.
Google always gets huge flesh from advertisers and throws few bones to the publishers..Yahoo and MSN common getup from asleep.