Here's an idea - aggregate debt at pennies on the dollar and sell it back to the debtor at twice the amount it'll still be pennies on the dollar and you'll make a nice profit.
That's essentially what a lot of debt collectors will accept. If you have debt in collection, sometimes you can offer them a lump sum instead of the whole amount and they'll take it because they're looking to simply profit.
At that point it's likely your credit is already ruined though... which is a whole different topic to broach.
In the UK at least getting passed to a debt collector should have no impact on your credit score. It's when they decide to go further and recoup it through court that you start to get hurt. This is my experience at least. It makes sense as I know many people who have been passed to debt collectors for debts they didn't owe so it would be a mess if that effected their credit.
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.