For me charging 25% to the contractor for the live of the contract is completely unjustifiable just for posting a job in some site and some emails and phone calls.
The recruitment agency gets money, because they've taken the time to build a relationship/do sales stuff/navigate a procurement department/convincing someone they can solve the clients problem (I need more resource!).
In the age of the internet, if a company needs some resources then the hiring manager could place the job description directly in some website instead of asking a recruiter to do it for him.
He can filter out CVs much more effectively by keywords using some GUI rather asking a recruiter to ask for the keywords on the phone.
He sends a mail/phones the candidate for an interview, how hard could it be? He needs to interview the candidate anyway.
I don't see how a few hours of administrative work for a hiring manager could justify the fortune that the procurement department will spend with the margin payed to the intermediary.