As always, whether we're talking about carrying nothing but $10 worth of water on the desert hike, or having a gas mask... its an optimization problem. Everyone has a different idea about what is the optimum for EDC.

And since everybody's situation is different, its possible for everybody to even be right (for their situation)! You live where the risks of terrorism is at their greatest level. You also live in a place where the cost of living is probably near the highest in the country. That means that the value of $100 to you, is quite different than its value to us. I think you should have a mask, just make sure you get a good one for yourself and your family.

If I were you, I would do the same. But for me, the money is better spent on other things. For example, that same $100 is a good start towards a backup generator for my house in the woods.