Apple - some good, some bad
Easily shippable devices like the Air are priced about the same as the US. A 27" imac has a far greater price difference. Since surface shipments go by volume rather than weight (mostly), there's still some gouging going on.
It isn't as bad as the local goods though. A nice Camembert shipped from France is a mere $1 more than the local brie. Stroopwaffle shipped in from Holland is the same price as those made down the road in Victoria.
This is not "made in sweatshop in the Philippines vs expensive 1st-World labour" price differences. It's just food importation is made awkward by our local laws and geography and your going to pay dearly for it.
Billington's Mollasses sugar, (small box) is $5.39/£3.47 vs 98p in sainsburys. There are no other option for mollasses sugar in Oz. Ah yes, England, that major sugar-producing country... bananas are currently £9.50/kg vs £0.68/kg in the UK, sweet pineapples x2 £3 the UK vs £6.40 in Oz, rice pudding £2.20 vs £0.84 and my personal favourite, Bendicks mints. £4.09 in Sainburys, yours for just $42/£27 at the local shopping centre sweet counter!
Australian GST at 10% vs UK VAT at 20%(?) has little to do with anything. Prices on a some IT things have dropped as the AUD increased in strength, but on the whole things are similar to when it was 2.7AUD/1GBP and now it's about 1.55AUD/1GBP.
I would just like to say a big "thank-you" to Costco for coming to Melbourne and extend my extreme disgust that the Royal Mail no longer ships surface mail around the world.