Also remember, you would be serving Australia only from Australia. if I'm
not mistaken, the Australia backbone is more or less volume based
AARNET is the Academic and Research Network, it's not "THE" backbone. (Note: in previous incarnations many years ago it was).
Australia is an island, approximately the same size as continental USA but with only about 22M people. It's not really on the way anywhere, so the submarine capacity is pretty much limited to what is needed to serve Australia.
There exist various submarine cables which go North to Guam and beyond (AJC/PPC1) and East from Sydney (SCCN, Endeavour) as well as SMW3 from Perth to Singapore. SMW3 is a great path into Singapore, except it's old and capacity is limited. Another cable is meant to being built on that path - many people have tried, let's hope the next attempt will work. Connecting these we have really only four sets of land based networks (Telstra, Optus, AAPT, NextGen - not all of these have complete coverage and/or rely on others for redundancy). We're very like Canada in some ways - small population along and edge (Canada is the US border, we're along the Southern and Eastern coasts).
Various providers have capacity on different sets of cables. It's difficult to generalise as, for instance, some providers use the cable into Asia to provide business customers with good connectivity but don't generalise that to residential customers. The kinds of connectivity at the end of those cables varies as well.
If you want to get content into Australia then generally to get the best delivery:
a) Put it on the West Coast of the USA - LA or San Jose - everyone has good connectivity to those places. Look for places you can easily get content into AS4637, AS7473/7474, AS4826 and AS4739. AS4648 for NZ and some of AU as well. (AS4739 will peer with you there (*)
b) Deliver it domestically in Australia in Sydney. Equinix Sydney is a good place to start. You can get domestic transit as well as good peering to most providers. It's also close to the large population centres on the East Coast (SYD, MEL).
c) Failing that - try Japan first, then Hong Kong then Singapore. But you will need to combine with a) or b) to give good connectivity to all providers.
Consider various acceleration things like CDNs - especially LLNW, AKAM and EdgeCast who all have delivery capability in AU already.
If anyone has any specific AU questions then I'm happy to try and answer off list. (I work for AS4739 and am responsible for peering and transit so have reasonable interest in delivery of content to customers in AU - we're keen to have GOOD connectivity).
(*) AS4637 has AS1221 behind it, AS7473 has AS7474 (their customers are in AS4804) - they have around 50% of the market together in terms of traffic delivered to the AU market. Tools like peeringdb.com<http://peeringdb.com> and bgp.he.net<http://bgp.he.net> will tell you how everyone's connected.