Originally Posted by GUWonder

CPH-US-CPH has been going for around $180-$280 roundtrip for September travel dates in economy class. The one-way ticket prices for CPH-US have been way more expensive for the same dates as the CPH-US part of the CPH-US-CPH tickets. Can't speak as much to the premium economy prices, but buying up on the economy class tickets can work wonders at saving money at time, but it may require a gamble of ending up in economy class.

With throwaway-the-return-part of the roundtrip tickets, a very useful approach can be this: pushing out the return trip date to the furthest possible date that still gets the cheap price.