Attackers aren't paying with their money, but it's important for them to go undetected. If your bandwidth is a fixed cost (ie isn't related to your actual usage

Attackers aren't paying with their money, but it's important for them to go undetected. If your bandwidth is a fixed cost (ie isn't related to your actual usage) you are much less likely to keep an eye on it than if it costs an arm and a leg.