Imagine how well it would do without all the baggage its carrying now.
It's carrying baggage both on the ground, political appointees (prev-i-usly dis-udvantaged) and in the air (friends and family of the former on freebies and rebate tickets filling seats in the front end. That's why BA can make a profit on the route and SAA can't. SAA's aircraft are less economical but not to such an extent.