Indeed if it was that cheap I wouldn't bother but unfortunately in August a return SIN>DRW Starter fare is $595 SGD and there are four of us so it adds up. Plus its probably worth paying the extra $60 SGD on each fare to get the extras (might have to change the date) so it becomes $655 SGD per person.
I thought about a redemption booking the one way that was available (DRW>SIN) but the taxes themselves added up to about $242 AUS. In fact, now I think about it, I don't really understand how that works. The price of the ticket on Jetstar one way is only $258 which is just $16 more than the taxes. Those Jetstar prices do include taxes, right?