I like to keep tabs on what homemade soda information is available on the web. A couple weeks ago I found this article from the Christian Science Monitor by a Trent Hamm. It talks about the other costs associated with drinking homemade soda, particularly health costs. In my opinion, it seems a bit narrow minded and kind of misses the mark.
I agree that drinking that much sugar is not anything near healthy. But there are some calculations in the article that could use a second look. The article compares Sodastream cola to Coca Cola. First, let's look at the financial aspect: The article says that using the Sodastreams syrups you spend about $0.40/liter. One thing they forgot was the ridiculous amount you end up paying for a cylinder exchange. Generally, about $15 per cylinder which works out to an extra $0.25/liter. So sorry kids, you're spending $0.65/liter for Sodastream beverages. Compared to the $0.70/liter for cans of Coke. So you'd have to drink 1600 liters for you to make the initial machine investment worth your while. You'd be way worse off in reality than what you thought following Hamm's method.
As far as the health aspect goes, what Hamm doesn't realize is that each serving of Coke has 100 calories while each serving of Sodastream Cola has only 35 calories. 27g of sugar compared to 8g. So in reality, you'd only be consuming 112 lbs of sugar from that amount of Sodastream cola rather than the 380 lbs of sugar you'd consume from that amount of Coke. Hmm... that sort of waters down his claim about the health consequences of the Sodastream. Even if it is still more than Hamm's original estimate, it's actually sort of a selling point for the silly little contraption. Though, that's still a ton of sugar.
Perhaps the best way to look at it economically are the following two scenarios:
Club Soda - For some strange reason, I can't find a decent sized bottle of seltzer anywhere in this town. The largest bottle I've found is a 1L, and the cheapest that's been is $0.50. Now I know there are companies that make 2L bottles, but I guess there just isn't a market for that here. Anyway, The soda stream could carbonate water for $0.25/liter as noted above for cost of the CO2. So you'd have to drink 320L of club soda to break even on the device. Plus, no significant negative health consequences. That's still a lot, but not as bad as the cola.
And since I'm by no means trying to sell the Sodastream to anyone, let's look at my method: the soda keg. I can carbonate water for about $.09/liter. However, I paid more for my setup, so I actually don't break even until I hit 365L of club soda, so kind of a bummer.
Gourmet Soda - Coke is like the Buick Century of sodas. It's a staple. Decent, but ubiquitous and thus, inexpensive. In fact, some places use the name Coke to mean any type of soda. What Hamm doesn't take into account is the quality of homemade soda that equipment like this can churn out. What we're looking at here is a not a way to duplicate the Buick, but a way to build our own Alfa Romeo. I'm going to consider a recipe from Andrew Schloss that in my opinion is even better than an Italian import, San Pellegrino Limonata. I can buy a six pack of 330mL cans of Limonata for about $6. That's about $3.03/liter. Ouch! But, honestly, it's worth it. Schloss's recipe in my setup gets me a better product for about $0.99/liter. Huzzah! So I really only have to make 144L of that for me to break even on my equipment or 42L on the Sodastream... interesting. Additionally, when I can make something that good, I'm going to want to share it so I can show of my beverage making skills. So I guarantee that I won't be drinking it all by myself and I won't be shouldering that health burden of all those extra calories alone.
The bottom line: soda isn't the best choice of beverage, but if you want to make it yourself, you do have a little bit more control over your finances, your health, and the quality of your soda compared to drinking standard commercial fare.