Points earn BNE > MEL half of MEL > BNE?

[btau]

I seem to be getting some pretty massive variance in my points earn at the moment.
Here is an example, both were "business saver" & both were very similarly priced:

18th March Brisbane to Melbourne: 60 Sc's, 3945 earn, 3945 bonus, 7,890 total.
19th March Melbourne to Brisbane: 60 Sc's, 7,890 earn, 7,890 bonus, 15,780 total.


Last month the same thing happened:
25th Feb Brisbane to Melbourne: 4,310 earn, 4,310 bonus 8,620 total
26th Feb Melbourne to Brisbane: 8,620 earn, 8,620 bonus 17,240 total

I don't get it. I'm booking the same fair classes as far as I know both ways & paying very similar amounts - why am I getting half the points on BNE > MEL that I get MEL > BNE?

 

[markis10]

Its based on what you pay, 5 points per $

 

[notzac]

18th March Brisbane to Melbourne: 60 Sc's, 3945 earn, 3945 bonus, 7,890 total.
19th March Melbourne to Brisbane: 60 Sc's, 7,890 earn, 7,890 bonus, 15,780 total.

I've noticed similar sorts of things before; I think it's down to how they allocate $$ to flights in an itinerary more than them not giving you enough points. 3945 + 7890 = 11835 / 5 = $2367 spent on the entire itinerary (not including any extras purchased as a part of the trip). If you spent substantially more, complain ... if you spent less, keep your mouth shut!