Of security systems and RFID

I recently toured a newly renovated academic library (very impressive: over 130 workstations plus wireless laptops to checkout, plus a Starbucks). The materials had never been stripped for a typical electromagnetic security system, and the staff had considered adding that or an RFID system. In the end, they opted to budget to replace any items that disappeared, and see just what the lack of a system would cost them.

It's an intriguing idea and question: just how much does the average library lose (without a system), and does the system pay off? I know what the industry will tell you, but the truth of the matter could be quite different. And again, situations differ, but I wonder if anyone has really established such a record of loss to absolutely justify adding a system.