I still haven’t got one yet
Do you think it works out cheaper than buying the 90c 1.25l bottles of Soda water from coles and woolies?
Hard to say as I've never done the maths.
Refill gas is like $30 and does like 60L or so.
Each plastic bottle holds about 1L and works out about $10 each
Each flavouring is about $7 and 440ml and makes about 10L of flavouring.
So based on 60L (if my maths isn't fucked):
$30 + $42 in flavouring = $72 per 60L.
So $1.20 per litre.
However that highly depends how much carbonation (if any) you use, and how much flavouring your use. I find the default flavouring is way too strong and use half, and don't always carbonate.
Based on that we'd probably be:
$30 + $21 = $0.85c
and if you aren't using flavouring and only using sparkling water about $0.50 per litre.