But if he is getting ads from spyware it should be higher than what he has so far. I'd reckon it was one of the higher paying keywords, like poker
Maybe its a poor niche, or maybe its invalid clicks. Either is possible. Smart-Pricing is also a possible cause.
I think that is really quite low. But perhaps there are a lot of factors that would affect the earnings. An obviously they have been answered already... the keywords. I have a friend who actually uses lesser adsense on his blog or website and its earning him quite a lot. But I am not sure if putting to much adds would also affect the earning per click. Hopefully someone could also give an idea.