Mixture and ExXB, I was not talking about how airline pricing works. I am well aware of how it is done (in principle). The Economist article linked in my OP (which Mixture still evidently hasn't bothered to read) has quite a good explanation of how the A-B vs. A-B-C pricing difference eventuates.
I was talking about how it appears to the average punter, who couldn't give a toss about the arcane practices of airline revenue management, but sees nothing wrong in using only a part (A-B) of what he or she has paid for (A-B-C).
And mixture, are you still maintaining that hidden-city ticketing is fraud? No doubt you can quote cases, judgements, etc, to that effect?