It was my understanding that US Air no longer played the game of doubling (or more) the price of one way trips vis-a-vis that same flight as part of a roundtrip.

I just went to price a roundtrip flight and the outbound was a good deal -- the return was not. So I figured I'd just buy the outbound for now. When I went to book a one way, the price doubled and was coincidentally the same price as the roundtrip (if I had chosen a cheaper return flight).

When did this change? Or was it always like this and my original understanding was wrong?