Tangan, I suggest that you read what Virgin Blue actually did.
They did not reduce their surcharge BY $19, but by 20% TO $19. That means the surcharge reduction is less than $5.
Using your figures for the full fare economy 2% and 3% reductions, being $7 and $10.50 you have, in fact, proven that on a full fare economy ticket, Qantas has reduced it by more!