You'll find that DVD's are nearly twice as expensive as DVD's in the US. Streaming services are extremely limited and even more expensive than DVD.
Definitely agree DVDs are way more expensive there. Although, for rental it seems like both streaming and DVD rental are about $5-6AUD.
Again, I'm wondering what Australia you're talking about here. 2nd hand sales are perfectly legal, I can sell my entire DVD collection, I can even sell my Steam account, hell unlike the US grey importers operate openly and legally in Australia. I can buy a pallet of DVD's in China and sell them to Australian customers with no problems (well I have to pay tax on my sales, like all businesses). Only certain products are prohibited from resale such as even tickets (to crack down on scalpers), sensitive technologies (I.E. military tech) and perishable goods. I can put a half bottle of Vodka up on Gumtree if I wanted to, the only restriction I have is that I cant sell it to minors (the drinking age is 18 over here).
You cannot, however, rent your DVD collection in Australia. That's what I am referring to.