Back in 2006, when Germany was hosting the World Cup soccer tournament, a terrorist attack was narrowly averted. With bombs hidden in their suitcases, two men in their 20s boarded commuter trains in the city of Cologne.

Richard Barrett was on a U.N. team that tallied up the costs of terrorist attacks, including that 2006 attempt in Germany.

“These suitcases were meant to blow up a train and clearly that would have created a huge amount of damage and public anxiety and so on for very, very little cost,” he says.

By very, very little cost he means less than $500.