Aussie here. The Australia Tax [1] is absolutely a thing here: for example, it's difficult to buy decent kids' shoes for under $100 (!), whereas you can walk into any Payless in the US and walk out with a decent pair for $25 or so. Check this out if you don't believe me, and note that this is not a high-end retailer or anything, it's a chain with an outlet in every suburban shopping mall in Australia:
https://www.shoesandsox.com.au/school.htmlThere's a huge slew of reasons for this, but it's a sum of very high rents and wages, a small market and a general lack of competition. Ebay, Aliexpress and Amazon US are consequently very popular, but most retailers are international so shipping is slow and, for anything bulkier, quite expensive. (Also, the deals aren't quite as good as they used to be since the Aussie dollar has depreciated against the USD.)
So, if Amazon can build a local operation here that -- for the first time in Australia -- has the trifecta of low prices, wide selection and fast shipping, they will crush the competition, online and offline. Which is why local retailers are scared shitless.
[1] https://en.wikipedia.org/wiki/Australia_Tax