Flag carriers are generally more expensive for departures from their home country than from the destination country. For example, I've just done a quick search and the cheapest J class fare on CX for HKG to LHR on Friday 18 November is HKD 38,690, while CX LHR to HKG is GBP 2766.45, around 30% less.
Popular HKG to Europe expat routes at the moment for cheap J class with good service amongst my counterparts seem to be via BKK on Thai Airways and Vietnam Airlines via SGN (current J class fare HKG to LHR for same dates HKD 23,747 and HKD 25,711). Obviously there is a layover, but most people who do it usually stop off for a couple of days before travelling on. Neither is part of One World though.