I was just pricing up a LHR-PER/SYD-LHR in W. BA comes up at about £1450 with all flights on QF metal but BA flight numbers. The same flights with QF flight numbers comes to about £2,400. Is this common? I'd much prefer the QF flight numbers to get my 4 sectors in for this year, but at the additional cost of £1,000 I'm tossing up whether its worth it or not. I've only looked so far on ba.com and qantas.com. Any other suggestions?

Thanks in advance.