I know a lot of you colleagues on here say P+P, points plus pay as on the QF website, or pay plus points (piss take), is not a good way of using points, 0.007 cents per point, but in my case, its the only way to do it to retain SG.
I used 5000 QF FF points to reduce a $750 J fare, MEL - SYD dom, to $715. $35. $35/5000 = 0.007, or 5000/$35 = 142.85.
With this, I get to feel what J on the 330 is like, get to access the J lounge at MEL dom, ... etc, etc, etc... most important, get J SC MEL - SYD meaning 40 instead of 10.
I pay a lot of bills with QCC, don't have a true credit card, don't fly on business, so have no other way of using the points.
If I go the way of the award, as the OP wants to do, I could buy an O class fare for $189, and use about 15000 QF FF points to upgrade, if there is a spot/slot, then I get J service, but O class SC.
$561 difference between $750 and $189, and using 15000 QF FF points as calculation, ratio goes down to 0.0374 and 26.73.
I know its not a lot of sense though, but in my case, P+P is the best, for others not so.