I negotiated for a friend in a small ransomware case. They paid $2k. Yes, reputation is important, I did some research to check whether others had successfully negotiated. If you get a reputation for not delivering nobody will negotiate with you. Likewise if you have a good reputation the amount of money people are willing to risk on getting their data back goes up, and that's good for business. It's also a reason why the ransomware was very clearly branded.
It's criminal but the principles of business still apply.