Value for money is something which ultimately only you can assess.

But here are a few more things to think about:-

1. [*]
2. [*]
3. [*]

I throw these things in, in case they might tip the balance one way or the other.

* Definition:-
- Adelaide, Brisbane, Darwin, Melbourne, Perth or Sydney and London or Frankfurt via Bangkok or Singapore
- Adelaide, Brisbane, Darwin, Melbourne, Perth or Sydney and Bangkok or Singapore
- London or Frankfurt and Bangkok or Singapore