Fares announced. Below are A$ fares.
Seem very similar to one stop Perth-London fares on QANTAS, and Gulf carriers as far as I can see, so no apparent premium being charged.
"Fares will start from $2270 for a return economy fare, $4250 for premium economy and $9725 for business class,...."
Qantas Perth to London non-stop flights on sale: Prices from $2270 return