The graph below breaks down the cost of terrorism in each European country as well as the collective cost on Europe as a whole.
The UK, France, Spain top the least, each occurring over $40 billion in terrorism relates costs. Altogether, terrorism cost Europe over $185 billion over the course of a dozen years.
This cost does not weigh a drop in social capital, which is a bit more difficult to measure. Nevertheless high levels of terrorism are correlated with a drop in happiness levels, lower levels of trust for people, the political system, politicians, and police. This merely touches on certain areas of social capital, when many aspects are likely also affected.