When I sold my DSP5000s to Struttmaster if I remember correctly there was a ceiling on the value before the transaction incurred some sizeable taxes. I think the limit was £500 (not sure what that was in Australian Dollars?)

Sending from the UK I didn't have to calculate the tax, just state the value of contents on the customs declaration. The buyer was responsible for import duties and taxes.

Lounge: DSP5200, 518
Snug: DSP33 x 5, C61R, HD621
Office: M33