Using my Citibank debit card, the final price I've been charged for ordering through the Microsoft US store is $65.96AUD (~45% discount from the full Australian price of $119.90).
There currently appears to be no restriction on the number of purchases (I've bought 2), however you will need to order each separately.
Billing may require a US postal address, I used a Borderlinx address which has worked fine.
The site says it can take 4-6 hours to process the credit card, however I was able to retrieve my code less than 20mins later (through email confirmation).
Discount should be available until 11:59PM AEDST tonight as part of Microsoft's 12 Days of Christmas sale.
I have been looking for a deal on Xbox music pass for a long time, this is great, just bought 2, thanks a lot NeoM.