Saving Tips for Business Insurance?

curious boss asks: "I have a question for the IT manager types out there: does anyone know how much a business can save on their annual insurance premiums by having their information security policies and procedures audited once a year? How much would an audit cost? I know those are vague questions, but if there's a rule of thumb (eg, cost per server, or cost per employee), or even pointers to getting more detailed information, that would be great."