We have one, definitely cheaper (and a lot easier than having to put it on the list). We use some of the syrups, but a lot of plain soda water that we add to juice or just as others have said, with slices of citrus, etc.

The gas canisters can be swapped at Big W and Target, those two I know at least. You'd think since we bought the unit from Woolworths you'd be able to swap them there, but I haven't checked. Costs about $17 for a 63L canister. Lasted us about a year.