There is a premium to be paid for being located in Singapore, and there is a premium to be paid for having a skilled workforce.
...
However, I think QF was hoping it would come cheap - and they are now realising it's not that much cheaper than back home.
They appear to believe it is cheap, thus offering such an appaling salary package. No mention of rent allowance ($3000-5000 per month required), schooling, medical, transport in Sin, etc, etc.
It may be cheap for qf/j* but anyone taking a postion there will ultimately pay dearly.
I very much doubt you will save much, if any.