This has got me studying the table with a bit more care. I noticed for the first time that the miles are (in most instances) for connections via Europe Zone 1. So I tried a dummy booking on the direct CX flight HKG/JNB and it spits out 70k miles. Pretty good deal.
Oh, and the taxes for HKG/JNB one way in J were a whopping ZAR350 (about 25 quid).