omg, they are nickel and diming you to death IMHO, 5-10 drops are just fluctuations, and will likely fluctuate back up in due time.
If You have EVER used adwords, you know just how much they are ripping the publishers off. I had a keyword I was paying .75 for, per click. I bet advertisers were lucky to see 5 cents
Is there a thread on that topic? I'd be curious to see a discussion on the differences between click payout vs. keyword cost.