For me, the value of a recruiter is that they're well-connected and can help with negotiations. It's icing on the cake that the company is paying them, not me. I would consider paying for this service if you were able to negotiate for me, and then I'd pay a percentage of the negotiated increase to you.

I don't really place much value on someone just applying to jobs for me - that part isn't hard. Now if you could do interviews for me...