I believe you've just described debt collection. The collections agency starts offering you to settle your debt at the highest possible amount and slowly negot

I believe you've just described debt collection. The collections agency starts offering you to settle your debt at the highest possible amount and slowly negotiates down. For any amount above $0 they receive from you is a marginal benefit for them. i.e. marginal benefit > marginal cost for any collection above $0 since buying their list of debtors is a sunk cost.