Thought of another possibility. Have it both.
They get the stealer free, when it steals the hashed info they can pay to have it sent to you for cracking, it will be a pay as you use service, so each crack will cost x amount. Only to be paid if you managed to crack it.
If the crack requests grew beyond what you could do then you could set up a sort of "Cracking partners" type deal.
Where people who can crack hashes will be sent the requests and they get a percentage of the payment upon success.
There's quite a few people out there cracking for free, so I'd imagine there'd be some interest, if it ever got that big.
Just a thought.