I think the main concern is - if you have a problem with them not
working or the speed is not what you expected - you can return them and
be covered under australian law.

There are quite a considerable amounts of local dealers who sell cheap
cards.

I have read Sandisk standard cards have progressed with speed increases
along with time. Depending on which camera, may be worth looking at.

They'll probably work just fine until your device tries to write past
the edge of the real memory space ... to the part that doesn't actually
exist! (say a 64MB card formatted so that your device(s) think it's a 2GB).

I have a couple of 2 gig SD cards here that have turned out to be fakes.  So far they work fine.

I have purchased SD card (1GB) and also CF card (1GB) thru eBay and they
both worked fine.
The price was good and the product has lived up to expectations.