Give them the money in cash , free the hostages, and then ten minutes later hit them with a cruise missile which will also destroy the cash
Simple is the best solution sometimes....
You won't know whom you hit. There are too many of them.
If they think they can get cash, it might embolden them to try such kidnappings again.
Send in a fully armed apache chopper with the cash, exchange it for the hostages and fly out
5 min later airstrike the fuckers from 60,000 feet with laser guided missile
They won't have actually gotten the cash (or gotten to spend it anyway
and you will have killed the right people and given them not much incentive to try that again....
Of course they will try other methods but for every problem theres a solution...