When the cost of security exceeds the cost of what's being protected, the solution need be reconsidered.
Similarly, the nude scanners would have done very little to stop the 9/11 hijackers, whose weapons were simple and equivalent weapons could be improvised from items that anyone can find on the other side of a checkpoint. Whatever we were doing in August 2001 to stop less-determined attacks was working back then and would work equally well today. The simplest conclusion is that whatever else is being done to stop a 9/11-style attack is working, and that the checkpoints are just a distraction.
Not that we should be surprised by that. The TSA was going to allow people to carry small knives through the checkpoints, and noted that you are already allowed to carry far more dangerous items through -- except for box cutters, because of their appearance. Then there was an outcry from people who are terrified of knives being on airplanes, and so the policy change never happened. With that kind of logic, it is a stretch to say that the checkpoints are keeping us safe.
In this case, by criticizing the spending of scanners as a deterrent to potential plots, are we not playing the part of CEO who complains about a small security expense as opposed to waiting until after a disaster to respond?