Some definitions need to be clarified here:
1) "Shipping" is defined as using one of them courier companies to send stuff from another nation to Australia. If it is commercial in nature (eg Amazon) then the value of the item has to be declared.
2) Bringing your laptop/notebook/desktop to Australia in your luggage is not considered "shipping" by Customs' definition. So no, if you bring your own laptop/notebook/desktop to Australia with you as you arrive in Australia, you will not be charged tax.
I have brought 2 laptops into Australia, where are purchase were worth about RM6000. Of course, don't bring in a bag full of computer parts: that's how you get pulled aside.
Another example: fellow friend brought a desktop from M'sia, which at time of purchase was valued around RM5000. Really, your more pressing concerns will be weight and how to make sure your desktop survives the journey.
Some discussion on bringing desktop's to Australia here:
https://forum.lowyat.net/topic/1286048/+13003) If you ship a full desktop/notebook/laptop over as a private individual, (ie asking your parents to send one over via DHL), generally you don't get taxed, even if it is a Alienware worth RM4000, as long as you declare it as a "gift".