GST plays a minor role - but you're right it is the total price that is important. Also the range of products
Recent purchases of mine:
Same shoes locally - $180 (but nowhere even stocks them - so have to order them in) overseas - $85 delivered
Camera lens - $700 locally overseas - $400 delivered via express post in 2 days
Cycling shorts (with inners) locally - no shops stock them or get these particular ones in - could order online from Aus shop for $180 +$10 postage! overseas - $80 delivered
adding 10% GST to any of these overseas purchases and I would still do it!