It was just to demonstrate a certain absurdity. No, that conversation might not happen, but the point was that the terrorist planners have objectives beyond "cause mayhem". And that increasing airline security costs probably don't even rank on their scale of worthy goals.
In Afghanistan, al-Qaeda is bleeding the USA of billions of dollars every month. But the article suggests that merely inconveniencing air travellers -- to the tune of maybe a few hundred million a year, widely dispersed -- might rank as an acceptable second best to a terrorist.
al-Qaeda wants 'The West' to fear them. People get scared of air travel every time there is an incident, even if that incident is a terrorism attempt that was caught before it ever got off the ground. If al-Qaeda doesn't have some sort of media presence, then people will start to think that they are a non-issue. Maybe al-Qaeda doesn't really think of things in these terms, but I have a hard time believing that they are all religious fundamental crazies. For them to be so organized, some of them have to be thinking on a more practical level.
In Afghanistan, al-Qaeda is bleeding the USA of billions of dollars every month. But the article suggests that merely inconveniencing air travellers -- to the tune of maybe a few hundred million a year, widely dispersed -- might rank as an acceptable second best to a terrorist.