PAXboy: As a further Observation, I note the continuing disparity in pricing of LHR~SFO/JNB. I checked these at the same time on the two British carriers. Travel distance to these being almost identical and yet JNB is always more expensive - in any class. Such is the power of the market.
Competition may be said to be almost equal as LHR~SFO has BA, VS, UA and JNB has the two Brits and SA on it every day, sometimes twice a day. Lucky old South Africa with all those folks who want to get there that they are prepared to pay higher rates. Mainly because, upon arrival, the cost of the holiday/business is much less than in the UK. Ergo people will pay more for the flight as it balances overall.
Just supply and demand, isn't it? As I understand it, the number of flights between the UK and South Africa is artificially limited by bilateral constraints, and there are few sensible non-direct routings. Although I keep reading noises elsewhere on PPRuNe that the bilateral is being renegotiated, goodness only knows when any liberalisation will take effect.
To SFO, on the other hand, there are lots of other sensible ways of getting there in addition to the non-stops, which probably offer capacity more balanced to the real market demand.
It was a bit of a shock, about six weeks ago, to find that Y seats to JNB for Christmas were already selling out on the most popular flights. Not even SYD is that bad.