Double cost per month only change is number of clicks.
Beginning in May of 2012 my average monthly cost has doubled. There has been essentially no change in CPC and more importantly, there has been no appreciable change in leads. Not sure of the cause. I'm already limiting my ads to a 13 mile geographic radius.
The only thing I can confirm is that I've received more calls from SEO vendors wanting to "Improve" my CTR for a fee that exceeds even my current AdWords monthly cost. I'm a one man shop
Any insight regarding how to improve would be appreciated.
Re: Double cost per month only change is number of clicks.
The conspiracy theory reg. SEO vendors you're slightly hinting to probably doesn't work because that would require a high level of organization work and the associated costs would perhaps be excessive. A plausible explanation could be based on changes in ISP ownership which then often entails changes in IP number distribution systems. (That could attach additional users to your targeted audience.)
So that to devise a feasible remedy we should know much more about your account. Your best option might be to seek professional help in case you have a friend you trust who could have a short look at your campaign.