The number isn't itself the important thing, it's the consequences of their actions on the world. I think we can agree that terrorism, and the world's reaction to it, is a pretty big thing.

[EDIT, in response to the two replies I've received so far: I'm making a pragmatic suggestion. In pragmatic terms what matters is whether the benefits, whatever their size, outweigh the costs. I suspect they might, and even incremental benefits are still benefits]