I am now in OZ. My daughter was borned in OZ last year.
In General, the big items like Prams, Cot, car seat are near to two times expensive than HKs'. These all are "made in China". If items "made outside China" very expensive. The small items are not too much more than HK.
I can see Pigeon only. Here Japan's brand is not popular. Not only talking about baby goods, any other goods from Japan are very few.
My son was borned in Sydney last year. There are very rare Japanese products in Sydney. I guess cos it is not popular.
To me, I think the baby clothing is cheaper than HK. & the size fits very well. However, we need to change the sizes often. Honestly, I like the OZ style.
I brought my Prams in Sydney. I think it is better compare to the same price in HK.
Also, the things are really cheap in the Financial Year Sales (June & July) and End of the Year Sales (Dec).
However, I really suggest you bring the nappies (New Born) to OZ. In HK, most of the nappies with the line shows when BB pees. However, most of the nappies in Sydney do not have this function.
My son born in Nov 07. All the baby stuffs are much expensive than in HK. Most of my baby stuffs are bought in HK. You would better bring basic baby stuffs e.g. milk bottle, sterilizer machine, Stroller