This paper by an Ohio State political professor puts an all new perspective on what it costs to protect us from terrorist attacks.  It's makes the following points:

1. The number of potential terrorist targets is essentially infinite.
2. The probability that any individual target will be attacked is essentially zero.
3. If one potential target happens to enjoy a degree of protection, the agile terrorist usually can readily move on to another one.
4. Most targets are "vulnerable" in that it is not very difficult to damage them, but invulnerable in that they can be rebuilt in fairly short order and at tolerable expense.
5. It is essentially impossible to make a very wide variety of potential terrorist targets invulnerable except by completely closing them down.

With the following implications:

1. Any protective policy should be compared to a "null case": do nothing, and use the money saved to rebuild and to compensate any victims.
2. Abandon any effort to imagine a terrorist target list.
3. Consider negative effects of protection measures: not only direct cost, but inconvenience, enhancement of fear, negative economic impacts, reduction of liberties.
4. Consider the opportunity costs, the tradeoffs, of protection measures.

Summary provided by Schneier on Security.  Even the Air Force is getting in on the act:

The U.S. Air Force has been trying to use counterterrorism funding to pay for "comfort capsules" that will allow government VIPs to enjoy "world class" travel on military transport planes, according to reports.
...
Air Force commanders tried to convince appropriators to let them reassign more than $16 million to the project from the "Global War on Terrorism," according to the Post. Lawmakers said no, but the paper says officials still used $331,000 in counterterror money to pay for cost overruns associated with their first-class cabins.

And people wonder why terrorism isn't taken seriously... because our government doesn't even take it seriously.