A friend of mine had to go to visit her daughter, a few years ago, at the oher side of France(don't remember the exact airports, maybe Chambéry and Nantes, some small places like that). But she didn't need a come back flight(they'd come back together with the daughter's new car). The one-way ticket was costlier than the 2 way ticket. She took the 2-way ticket, while never intending to go back by plane.