I say this because I imported a piece of audio equipment that was way over $1k and it didnt get hit.
I do get hit off ebay etc. obviously but for every order that is the least bit obscure it seems to pass. They should be hitting me because the invoice price is right there but its not like as if its an Nikon D1000 (for example) where they can google the local price.
I would have expected everything over $1k to get stung, in fact i budget for it.
I haven't imported anything for a while, which is a big change for me, but back when I was, it was under 10% of items shipped via post that would get GST applied. If shipped via courier it would be above 90%. It's been that way for many many years.
EDIT: I'll clarify I'm only referring to those orders over $1k that should've attracted GST