Best way to estimate CPC for client

what tools do you guys use to estimate CPC for client, or to come up with approximate budget for the client. I used to use overture bidding tool and in order to estimate the CPC for google, i used to multiply that cost that i got from overture times 3. The tool is down now, should i use google estimator tool and what about yahoo? I can see the google estimator tool is not free anymore. Please give me some suggestions is how to do these estimates.
Appreciate that!

Original post by skionxb