Undoubtedly you're turning away the best candidates and almost exclusively interviewing candidates whom have extreme difficulty finding work elsewhere; so much so that the applicants value their own time so poorly that they believe it worthwhile to interview for a job which may not meet their personal financial requirements. I'd strongly suggest you change your practices and observe the improved calibre of interviewees.
EDIT: Also, if you really want good candidates, stop using a recruiter.
EDIT: Also, if you really want good candidates, stop using a recruiter.