Q. Why do the airlines charge twice as much to fly one-way on international fares than they charge for a round-trip on the same route? What happens if we buy a round-trip ticket and simply toss the return ticket or cancel the return flight "due to sudden changes in our travel plans"? Will the airline sock us with the difference between round-trip and one-way?
A. To answer the first question: because they can? It’s probably because business travelers tend to use one-way fares more often than leisure travelers, and the airlines figure that business people can afford to pay more. It’s unlikely that anything will happen if you don’t use your return flight, but don’t buy it through a travel agency, since the airline might indeed go after the agency for the fare difference. However, they won’t hunt down an individual traveler who bought the fare on the airline’s web site.