The least expensive place around here (Seattle) is 2.03/gallon. That's $0.54/liter USD (0.72 AUD/liter).

Factoid: In the USA, gasoline/petrol is less expensive than one-serving size bottled water:
gasoline: $2/gallon
water: $3.81/gallon
(based on local Safeway supermarket price for a 20oz Aquafina bottle at $1.19. Perrier is a similar price).

Australia too: Bottled water: $1.50.

Of course, plain distilled or spring water is far less expensive, under $1/gallon. But just in case brand name water is better than the plain stuff, don't you think it's worth it? Same as with gasoline.