Officially according to the Geneva Convention which regulates most rules on international air travel, it is true that airline is only liable for US$20/kg. However, having said that, most airline will offer you a bigger amount then that, especially if you complain. In situations like this, it is important to raise the issues or else, US$20/kg will be all you gonna get. CX lost my mother bag once, and she got a US$800 dollar compensation for it... although, that barely covers her expensive suitcase... but that's more then the norm... so it really depends on how much you are willing to raise the issues to the higher level managers at CX who has more power to give a higher compensation. Also, complaining to Marco Polo Club help as well.

Note: I am not encouraging people to complain, but sometimes that's the only way to go. Once an airline loss your bag, they are now in defensive mode to minimize their compensation. Even CX do that.