Very cheap prices to Johannesburg from pretty much everywhere.
Perth to Johannesburg. $1312. Oct/Nov. Qatar Airways
http://iwantthatflight.com.au/x2PERJNB-Flights-from-Perth-to…
Brisbane to Johannesburg. $1379. Oct/Nov. Etihad
http://iwantthatflight.com.au/x2BNEJNB-Flights-from-Brisbane…
Melbourne to Johannesburg. $1354. Oct/Nov. Etihad
http://iwantthatflight.com.au/x2MELJNB-Flights-from-Melbourn…
Sydney to Johannesburg. $1396. Oct/Nov. Etihad
http://iwantthatflight.com.au/x2SYDJNB-Flights-from-Sydney-t…
Adelaide to Johannesburg. $1372. Oct/Nov. Etihad
http://iwantthatflight.com.au/x2ADLJNB-Flights-from-Adelaide…
Good price but would pay a bit more to travel more direct… $1448 BNE-JNB with AUH stopover (37hrs outbound). The $1379 is via Melbourne. On QF it's 17 hours for $1642, $263 difference.