Qantas please compare this thread with a similar situation with VA back in 2011. Compensation for an downgrade from J to PY was $2200, and the thread had only 11 posts before it was closed.
http://www.australianfrequentflyer....ty-gold-downgraded-buisiness-class-28934.html
Instead Qantas chose to refund only $700 and the anger/disappointment at your actions has resulted in 812 posts to this thread.
Qantas like many other carriers have chosen to concentrate most of their marketing/ enhancement dollar toward their premium classes, and at the same time trying to turbocharge their Frequent flyer Program by allowing many points to be accumulated and SC specials allowing elevation of more pax into higher Tier Status. Additionally capacity is being moderated or redirected to high season demand.
This means that demand for J seats (whether revenue or award or upgrade) is rising. (QF does have a superior product in this case).
This also means the risk if downgrade is not "extremely rare"
So J pax are now paying more upfront but they are also increasing the possibility of a downgrade or a denial of boarding due to overbooking.
So for QF pax the costs seem to be:
Downgrade: An "enhanced" refund of the difference between fare paid and a full fare price whY on day of departure ("enhanced" because QF says its over and above IATA guidelines).
Denial of boarding and rebooking to another day: Associated costs not covered by QF staying in a foreign port, lost wages, missed appointments etc etc.
A whY pax will never be downgraded unless there is a later Jetstar flight, they may have to wait till the next day or days to board.
Qantas premium passengers with Tier Status pay more but when downgraded, they will pay even higher costs if their cabin is overbooked compared with a discount Y best fare of the day non status passenger.