Good headhunters charge between 30-35% and they earn every penny because they deliver where others could not. So 20% is not “usury” as you put it.
In the gig economy, like what these websites represent, the headhunters fee isn’t a one time commission for finding a qualitied salaried employee like a normal headhunters fee, it’s a kickback for using the site unconnected to the value of the service actually provided (being a classified ad host).
My point isn’t so much that headhunter services are useless. They should be useless these days, but they are theoretically filling a market need. The point I was trying to make is that with these sites, a person’s skilled labor is being chomped on several times, and the real value of the labor isn’t being realized by the laborer and the real cost of the labor is inflated for the buyer. I hate thinking of a future where that is the norm. Technology should be eliminating middle men, not entrenching them.