It depends on the age of the debt and how many agencies it's been through. Medical debt is also much harder to pursue legally if need be, plus everyone hates the guys who sue medical debtors. So I never worked with it.

But I'd guess that direct from the client would be 8%, 1 agency ~1 year old debt would probably cost 5%, 2 agency 2 year old debt probably about 2% and then down to 1% and 75bps after that.

A lot of times you don't turn a profit working zeros. You barely make your money back and then turn a profit reselling it. Small margins but easier to work. Happier employees.