I don't recommend drinking petrol, but if you want to save some money bring it along.

Seriously, most locals either drink the tab water (cistern or desal based on where you live) or they reuse their gallon jugs at the refilling stations for $1/gallon. Today, I saw a boater bring 12 empty gallon jugs to the fuel dock and refill with that water for $0.20/gallon. Not a bad idea either.

Keep in mind, it doesn't matter what the price is on the sheet or online. After they assemble your order, they will ring it thru the same register system that is used when you visit the store in person.

Cheers,
Jason