Yes it is bloody expensive.
Hint: just had DS's school uniform list - polo shirts @$24 (£16) and I'll probably need 2 or 3.
My friend's DS here needs 100% cotton polo shirts - she has chosen to order them from M&S in the UK because she can get 2 for ~£5, plus £15 P&P to Australia - so she gets 2 for £20 and they're 100% cotton, while I have to pay nearly that for 1 polycotton one.
Variation in fresh fruit and veg prices is phenomenal - possibly the worst I've seen is grapes, which can go from ~$2/kg to ~$16/kg in a week. The supermarkets don't absorb the price alterations, they're passed straight on to the public.
Petrol is about the only thing that is still cheaper, but if you do compare it to the UK prices, then it's no longer that much cheaper because of the exchange rate. I've been coming to Australia since 1997 (when the exchange rate was, iirc, ~$4 to the £1) and petrol has always been the same in figures, penny for cent - so petrol in the UK should be around £1.50/L at the mo, as it's ~$1.50/L here.
Oh and the trains are cheaper. But not all of them. It might only cost me $11.40 for a return to the city, which is 2h each way; but if I were to take the train to the international airport from as few as 3 stops away, it would cost me $15 one way.
Even though the NMW is higher here ($15/h), it still works out expensive.
I still buy clothes and things for DS from the UK when we go back - not only cheaper but better quality! Underwear for me too; and casual shirts for DH all come from the UK. Books - either I get them from chazzer shops, bargain basement shops, Book Depository. com or Amazon.co.uk when they're doing their "no delivery charge" to Australia.
Friends of mine will buy large toys from American sites and get them shipped over here because it's still cheaper, even with delivery costs, than buying them here.
Rates and utility bills can be frighteningly high, depending on area - I am so glad I persuaded DH that we needed to get solar panels for hot water and electricity to keep our bills down, other people in my area have seen their electricity bills double this year (comparing same quarter with same quarter last year) - we'll have "paid it off" in less than 5 years at this rate.
Then there are all the costs that you don't have in the UK - health care costs, dental, bank charges (these are amazing! they charge you for anything they can think of!).