I just checked Sg to Sydney... flight tickets cost $270, taxes cost $543... total $813... not that cheap after all....
2 weeks back, I saw Qantas having a promotion, and direct flights from Singapore cost around $800 including taxes.
If you click on the details on Malaysia airlines on the taxes, it shows
SG Singapore: Passenger Security Service Charge SGD 28.00 each
AU Australia: Australian Passenger Movement Charge SGD 49.00 each
WG Australia: Safety and Security Charge SGD 2.00 each
WY Australia: International Passenger Service Charge SGD 50.00 each
YQ Admin fee, Fuel (where applicable) and other surcharges SGD 414.00
Now we know... how they charge low flight fares... by charging more than $400 in admin fee....