Pre-screening is nice, but not much of a value add. Sourcing candidates is the hard part, and this service can only present the candidates that have entered profiles. No outreach, no advertising at any level.

Perhaps C-levels are 20%, or maybe in the Bay Area, but the standard elsewhere is 15%.

fwiw 15% is really low in my experience, across a range of locations and hiring at all levels . More common would be 1/4 or 1/3 1st year salary, with 3mo trigger (or clawback)

Of course YMMV.

I am in CO, ~30% is pretty standard for anything in tech.