The valuation for the various buildings damaged around the World Trade Center complex was very high, and there was significant damage to the Pentagon. Now, as commercial property, the valuation on the WTC and attendant structures was very high, though most were never going to be sold as they existed to be rented (or parts of them leased). The Pentagon's repairs cost a lot too
Then there's the four aircraft, which between them account for a few million, and then the damage to things like cars, fire trucks, and so forth from the dust and collapse.
Now, that's damage to physical structures. As was noted, the stock market tanked, and while a tiny number of folk made a killing thanks to an already extant strategy which included put options, most made losses. Though that's imaginary money becoming smaller. Then there were projected losses, to tourism, and so forth, and the cost of a lost day of trading. A key economic lesson here, by the way is the
Fallacy of the Broken Window, which is a good introduction to opportunity costs. All the money spent on the War on Abstract Nouns is money that could have been used for other things, and since much of it was wasted on nonsense that's not insignificant.
The real cost, the monstrous economic damage, however, the one which directly affects America's net worth (or, more specifically, it quantity of foreign debt) is the price of oil, and in particular gasoline. America's consumption is immense, and when the price went up its consumption did not go down such that its balance of foreign payments remained stable (ie, Oil at price A times quantity B, giving AB as total, twice A, half B, it remains the same). That money goes abroad. Though a lot of that money isn't money, but debt. That's the real damage.
I'll stop before I start talking about coffee shops and money as information.
your sig x
