I’m working on that math right now. For me our local home brew supply says $13.85 for a 5# refill and $24.99 for 10#'s. 20# is $34 but that’s getting to be a pretty good sized tank (28" tall and close to 50#'s harder for my SO to refill for me 
).
I was using a higher price for the SodaStream tanks but even at your price that is a pretty big price difference.
I am planning on posting here with a more detailed comparison but I think we are thinking along the same lines.
Yeah, I’d looked into sodastram nearly 20 years ago and decided the sodastream co2s were a horrible deal (even with BB&B coupon which was thing even then). I was still strongly considering a purchase, but even then there were co2 adapters so you could buy cheaper gas in bulk. But not everyone is into breaking the rules or janky diy stuff, so no judgement!
I have an engineering degree, and like to think of all my saving money janky diy stuff as well researched and engineered solutions 
There’s nothing janky about running a bigger gas bottle on the Sodastream. If you’re comfortable screwing in a 60L bottle it’s not much different.
CO2 will freeze burn you if you’re stupid, but you can do that just as easily by pressing down the valve on the 60L refill.
Here’s my results on pricing in Aus.
60L refill $19. Approx 400g.
2.6kg bottle. $68. New purchase.
2.6kg bottle swap. $30.
Freedom one adapter hose. $50.
You get 6.5x the fizz from the 2.6kg bottle.
You pay off the new equipment purchase with the first 2.6kg used.
Ongoing costs excluding equipment are 23% of the OEM bottles.
Running kegs for water works well but you’ll need space in the fridge. The Sodastream machine in the pantry with a big bottle is a better solution in my experience.
PS. You’ll get roughly 1L of fizzy water per 6g of CO2.
I took a little time to come up with a few numbers & ideas. After a few hours of internet research and after reading some comments above, looks like a homemade kegerator is the way to go on this if you are a heavy sparkling water consumer, have the spot for it and some DITY skills to put it together. This wouldn’t be the on the kitchen counter solution but some people do have mini-fridge type keg coolers in their kitchen/dining rooms. I would put this in the garage.
Here is a cost breakdown assuming my math all checks out…
SodaStream
SodaStream Fizzi Sparkling Water Maker Bundle w/2 60l CO2 - $149
Total Startup Cost = $149
Price in 12 packs of La Croix @ $4.90 per 12 pack = 31 12 packs
Homemade Kegerator
STANDARD HOMEBREW KEGERATOR CONVERSION KIT WITHOUT TANK $98.99
5 GALLON BALL LOCK KEG WITH STRAP HANDLE $107.90
CO2 CYLINDER – 5 LB - Full $85.84
Used Fridge (craigslist) $200.00
Total Startup Cost = $492.73
Price in 12 packs of La Croix @ $4.90 per 12 pack = 101 12 packs
A mini-fridge will work as well and you could buy that new or used and reduce cost and size. I used the larger refrigerator in the cost calculations because I have the space for it. You can buy everything on the list on craigslist and go even cheaper.
| SodaStream Next 5 LBS of C02 All In Cost (I’m rounding up to 1lb per bottle) | $100.00 |
|---|---|
| Price in 12 Packs of La Croix | 20 |
| Volume of Carbonated Water Produced | 283 Litres |
| Home Seltzer Station Next 5 LBS of CO2 All In Cost | $13.45 |
|---|---|
| Price in 12 Packs of La Croix | 3 |
| Volume of Carbonated Water Produced | 283 Litres |
My assumptions are:
So for the long game and if you are a heavy sparkling water drinker, the Kegerator price gets very attractive after the initial spend. If you aren’t a heavy drinker, hard to beat the SodaStream and as @Rosscopeco mentions, you can put a bigger bottle on the SodaStream which would really tip the numbers in favor of the SS.
| Water Type | Per Ounce | Price Per 283 Litres |
|---|---|---|
| La Croix Price Per Ounce (ongoing) | $0.0340 | $325.55 |
| SodaStream Price Per Ounce (after initial spend) | $0.0105 | $100.00 |
| Homemade Seltzer Price Per Ounce (after initial spend) | $0.0014 | $13.45 |
| Water Type | Per Ounce | Price Per 283 Litres | 1st Batch | 2nd Batch | 3rd Batch | 4th Batch | 5th Batch | 6th Batch |
|---|---|---|---|---|---|---|---|---|
| La Croix Price Per Ounce (ongoing) | $0.0340 | $325.55 | $326 | $651 | $977 | $1,302 | $1,628 | $1,953 |
| SodaStream Price Per Ounce (after initial spend) | $0.0105 | $100.00 | $150 | $250 | $350 | $450 | $550 | $650 |
| Homemade Seltzer Price Per Ounce (after initial spend) | $0.0014 | $13.45 | $493 | $506 | $520 | $533 | $547 | $560 |
3 cans of La Croix per day for your household would be 388 litres per year. I think we go through more than 3 a day honestly with 5 people in the house.
I’m still slightly undecided but leaning towards the kegerator. 
Thoughts?
You need to factor in the cost of running a separate fridge.
A chest freezer with a temp controller is the best solution if you go down that path. Lots of insulation means they cost very little to run at fridge temps.
Another solution is to refill your own bottles with a bigger Co2 bottle. That does take a bit of skill though.
I have 2 mini refrigerators already full of water so for me I don’t think I’m going to mess with adding the cost of running another appliance. I also am not factoring in gas costs for going to the store to buy La Croix etc.
But I did look at some of the folks using deep freezers rather than refrigerators. Definitely looks like the most cost effective way of handling it. 
Looking better all the time!
I do a no-keg version of this-- mostly just to save trash from the plastic bottles or club soda cans-- and you can get it really fizzy, which I love
I’ve simply got a big 20lb CO2 tank, with the regulator similar to the one in the video which goes into that ball lock adapter. But instead of the keg I use a carbonation cap with diffusion stone which just screw into your plastic soda/sparkling water bottles.
I’ve got two of those carbonation caps-- permanently on two 2lt plastic bottles, then as one finishes, I refill, hook it up to the ball lock, turn it on, shake it to help the diffusion (or just leave it until I remember to unhook it).
That’s genius. So for the cost of a cap and a bottle of CO2 you have cold sparkling water for the time it takes to shake the 2 litre or you can let it happen on it’s own. So basically less than the cost of the SS but a little more work and it’s not a counter top option. Sounds pretty damn good. Thank you!
Maybe not the safest idea given the 700+ psi coming out of the tank. You could easily dial it down with a regulator though. 
It’s got me thinking now as I have all the gear for running kegs with the Sodastream bottles. That could make for a really portable unit for the car.
$12.92 at Bed Bath & B with a bottle exchange and 20% off coupon.
60L which is under a pound per above.
That’s solid, definitely hard to beat that. Probably the best way to go for most people.
I’m afraid I, as I usually do, went all in on the water making experiment. I will post pics when I get it all setup.
Awesome, can’t wait to see pics!
That’s pretty much standard pricing in Aus. Exchange rate factored in.
For once I’m not getting charged Oz tax.
I’m keen to see the setup as well.
Anyone else think this would go all Bear Grylls and be about drinking your own pee?
I use different filters for water cleansing. These are mostly based on minerals… For example, shungite minerals: Real Shungite Black Stone For Water | Karelian online Store
