You may or may not already know this. If you do, you are doing your job and you are prepared for the response and have the perfect candidate to present. If you don't, something is wrong with the way you're doing your job or the way your department is being run. In any event, your response is a bunch of information questions after getting the first teeny-weenie “yes”.
“Ads are certainly more cost effective than paying us headhunters aren't they? Do you have someone doing the initial screening? Whose idea was it for the ad? Who wrote it? We run ads too and they do take some time don't they? Do you find, as we have, that most of the replies are not the most qualified? Our purpose of running an ad is name recognition which helps in recruiting the top notch candidates. Does someone at your company invest in recruiting by aggressively calling people who have not responded to an ad? We have also found that the top people never respond to ads; they always seem to get their positions from someone calling them. How about this -- compare your ad response to my one candidate and tell me what you think? We often work with clients who are running an ad, because it costs them nothing to look at our people and it gives them a first hand opportunity to make a comparison.”