If u earning oz dollars then it would be best to buy there.. One thing which does make it cheaper is you do get nice specials. Eg Dell stuff with coupons if i remeber correctly.
I remember one deal a while ago(a few years) where u could get a dell 30 inch, and a free 7800 gtx for 1800 aus dollars or something, i may not be remebering right. But a free top of the range graphics card is not a bad freebie.
If u going mac, then dont bother , macs are very expensive in aus.
The average salary in aus is 39000 aus dollars. It can quite easily be much higher than that. Professionals can earn a 100 000.
That would mean u could buy a dell 27 inch for about a weeks work, depending on salary. I dont think the average south african could do that.
http://www1.ap.dell.com/content/products/compare.aspx/30lcd?c=au&cs=audhs1&l=en&s=dhs&~ck=mn