You don't need to look at the books for that. Imagine you got that offer. Millions going through the accounts that you have to protect, secure in online and offline environment, monitor, ideally have complete control over access logs, think about relevant company certifications that may be required because you deal with money one way or another. And you need to have some practical banking knowledge on top of that. If anything goes as bad as it did, it could be your name in that article instead of the company owner.

With no inside knowledge of the books, how many people would you think need to be on the security side of that company and how much would you request to get paid? I'd definitely go with (10+)x amount a very well paid person gets in other companies.