Often we will chat to a hiring manager who's vacancy has been open a few weeks and in some cases a few months. The company has advertised it's role, put it on the company job board and given the role to all the recruiters on it's preferred supplier list. When choosing companies for the preferred supplier list, recruiters who charge 12% are selected ahead of those that charge 15% or higher. No focus is placed on what you should really be judging, does your recruiter know your niche, does your recruiter stay in regular contact with candidates within that niche and will they provide you with 3 or 4 quality candidates that you can interview next week?
Every person in your employ should be making money for the company, if they are not you should not have a vacancy for that role. A candidate's cost to your organisation is at least his or her basic salary and their weekly cost is 2% of their annual salary. Most experts will tell you that you should be getting 3x the salary as a return from your employee, that takes the opportunity cost of an employee to 6% per week. Any savings in doing the hire yourself or going with a provider who charges 15% instead of 25% are wiped out in a few weeks if the hire is delayed. Measuring your recruiting process by how much it costs you is the wrong measure.
We all know that great employees are worth way way more than their cost. So fees aside, you as the hiring manager want to be interviewing a selection of the best possible candidates for your role not the best possible candidates who saw your advert. Judge your recruiter by how quickly they can arrange 3 to 4 interviews for you of suitable, quality and qualified candidates. That's what your vacancy is worth!