Impact of Attacks and Outages

Hi, Is there any paper/link that discusses the financial repercussions when an ISP's network goes down because of an attack/outage? What i am looking at is something that i can explain to a lay person, about why the networks need to remain secure so that they cant be hacked into, as once it comes down, not only does it impact the ISP but also the enterprises inside that service provider's domain. I tried googling but couldnt really come up with something. Any help in this regard would be really appreciated. Glen