I upgraded yesterday from super-inflexible business (I class, booked in the Black Friday sale) to First at Heathrow for £500 one way. This as part of LHR-CGK-MEL with 6hrs at CGK, with the full F service from plane door to lounge etc.
I also overheard someone else say they were offered (and declined) £429 for economy to business.
Last edited by dsf; Jun 28, 2017 at 8:45 am
Reason: added Y->J price