That's assuming one uses the $5 off coupon at BBB. It also doesn't include the cost of the machine. But, my main point of posting was to give people info that the 130L doesn't actually last for 130 bottles.
Since you are going 10 digits after the decimal point, might also add the cost of the water/sewer charge, And if you're going to BBB you must add the cost of Gasoline, and car wear/tear.
And don't forget to add the cost of the bottles.
And if you really like your seltzer strong, you would go beyond 3 buzzes, changing the math altogether.
I have a SodaStream machine I got as a gift. I've stopped using it as I've found it too much of a hassle (especially since we easily go through 8-12 liters of seltzer per Shabbos, and about 1-2 liters a day during the week) and I've always doubted how much it really "saves".