That's just the number on wikipedia. 430,000 people lost their jobs in the 3 months after the attack. I supposed you could argue that it's not direct damages in the sense that 430K people were not all office workers in the WTC, but if they lost their job within 3 months of the attack it seems like the job loss is pretty directly related.
And, as a former NYC resident I would not at all be surprised if 430K people really did directly lose their job. The sheer number of people working in that area is immense. I remember an interview at the time with a guy whose bodega located down by Wall Street was destroyed, and he said he did $80K per week in business. And that's just one dude selling sodas, bottled water, cigarettes, etc.
In other words, imagine a hypothetical world where the reaction to 9/11 was "damn, let's figure out who was behind this, go arrest them, and rebuild and carry on with our lives" rather than the "holy shit, let's declare a war on terrorism" reaction that actually happened. Do 430,000 jobs still get lost? No, I seriously doubt it. You lose some jobs because a bunch of office space got destroyed, but most of those jobs are still needed and will simply be relocated.
The financial markets depend upon stability and law and order. They cannot function without it. The fear that markets and industries could be crippled with a simple bomb (not due to the reaction, but due to the event) did massive damage to the markets, which resonated and caused significant economic collateral damage. This is obvious given that the reaction to 9/11 was actually quite sedate for some time, and massive enterprises like the NSA's current adventure came about much later.
If the NYSE building were bombed on an operating day, it would absolutely have dramatic financial repercussions, and that market would absolutely be crippled. Would some simile reappear? Of course it would, just as government would reappear if a full capital building were attacked. But the impact would be major and it would be felt.
No, 300bps, 9/11 brought a sense among both the populace and business that big, bad things can happen by just a few people with ill will. The response was a realization that the basic security and law and order could be so easily overridden.
But good effort, regardless.
Obviously 9/11 didn't start the Iraq War, President Bush did. He may have done that in a state of belief that the two were connected, but we should not repeat his mistake.
It seems odd to me to lump in how much we poured into terrorism over and above the direct damages, and not to lump in with car accidents how much money we pour into auto safety, road maintenance, and so on.
The general point is that we over-respond to trauma, both in our daily lives and a macro society level. Clean living is more important and has broader effects on your life than crime, but it is less sexy on the evening news. Just like car safety and terrorism.