I've gone throught the email conversation, i feel like they didn't really just wanted the money. A blackmailer don't just ask:

"SO  - you told us a week ago that you've being requesting a    response from Fin dprtmnt. We got no answer for the below question    so far:            ?How much do you consider ENOUGH to pay us in order to            work all the issues out?

"

He know what the value of what he got.