It'd be interesting to know if those profitable job boards are profitable because of recruiters paying and re-posting the same jobs (changing few words here and

It'd be interesting to know if those profitable job boards are profitable because of recruiters paying and re-posting the same jobs (changing few words here and there) in order to gather CVs. I was looking for some statistics about the ratio of a real (as posted by a company) vs recruiter job post on those job boards, but I couldn't find anything.