Australians are required a valid visa in order to travel to Vietnam. The cost for visiting an embassy to get a visa  will be 70 AUD, and takes around 5 working days to get your visa approved.

Visa on arrival - Visa at embassy comparison chart

Besides from getting a Vietnam visa in Sydney or Canberra, you can also apply for a visa on arrival as it seems the cheapest and easiest way to get a visa to Vietnam. Click here to see how it works.