L-188: Well, the reason why it is cheaper for Airbus is because they cleverly outsourced the designing, building of the 4 aircraft to a custom-founded subsidiary company. That way, Airbus just paid the price of purchasing 4 aircraft and the maintenance, but the design & construction were done in a seperate company that, I believe, no longer exists. Some clever accounting, I suppose.
Now once the planes are there, transporting a large section from here to there is costly, more so than on ship or train, I would guess, but in the overall aircraft production cost it becomes negligible. If Airbus really does have a lower cost base, (which I do not know anything about), then their employees are probably more skilled and productive (read: they have less employees and more automized processes, and train their employees to higher standards so less waste & mistakes occur).
If you hire&fire as Boeing does you can deal with boom&bust quite well for a while, but it the long haul, you are likely to have less skilled employees (because you cannot invest years in their training) and less motivation, so eventually you end up with more employees per plane produced. And the zero-defects thing is harder to achieve, too.
DISCLAIMER: I do not work for Boeing or Airbus nor am I familiar with their books and efficiencies, I am merely stating thoughts & considerations, not based upon any numbers I have available at the moment.