We were spending $70,000/mo+ on Adwords. When the huge Panda updated occurred around March 2012 it bumf**ed us big time sending all our keywords right to the back of the serps. We dropped spending to $5k/mo. The rankings have recovered but our spending is way down, this month the bill is about $3k/mo.
The only advertisers in my niche these days are huge companies that don't really monitor their serps conversions because if they did they would realize they are losing money on each click.
So Google reports that clicks are up but price per click is down.. The increase in clicks is most likely attributed to YouTube showing ads on nearly every single video recently. I've NEVER clicked on a YouTube ad on purpose, however I have clicked on them accidently when trying to get rid of the annoying ad.