Great thread. Thanks to the OP and subsequent posts that made it easy to understand the 'Cash & Points' option.
Just booked two round-trip Business Class seats SYD-PER for a total of 27,600 points and $672.98.
Compares very favourably to the full fare of $5,596 or a points redemption of 146,800.
You're very welcome - I'm glad what looked like a quirk in the redemption process has led to some terrific deals being discovered and shared around!
Would love to book an A330 J MEL-PER at these low redemption prices - now just need to think of a reason to go to Perth (have absolutely no reason at the moment!)