Comparing your costs to the costs of a manufacturer isn't really accurate. It's about what you're spending on soda stream vs what you would otherwise be spending on sodas.
Well, yeah. Point being that Coca-Cola can provide you with soda for the same price or less than you'd be spending on ingredients. Scanning Peapod, a 2 ltr bottle of soda is $1.00 to $1.60 so 50¢ to 80¢ a liter depending on how brand conscious you are. Probably get it cheaper by not shopping on Peapod but whatever.
I'm not against someone owning a soda machine (that would be weird), I'm just saying that it's like home brewing or a bread machine or something -- you do it for enjoyment and potentially a fresher/better product, not because you're going broke buying $1.09 loaves of Wonder bread. Edited, Jul 1st 2013 9:55am by Jophiel