Based on the $160,000 you posted in the OP consider this hypothetical
Tax Rates for basis of calculation were found here
ATO Individual Tax Rates 2011/12
Please note this example is very simple, and takes on-board a few assumptions.
I have not taken any consideration into the application of Medicare Levy.
Please also note that legislation is prone to change which may deem the variables used to be obsolete.
Summary:
With Deduction: $5,700
Without Deduction: $9,550
Difference: $3,850
Cost of Difference: $10,000
Opportunity Cost: $6,150
This post is not to be considered 'in any way, shape or form', as advice.