Coincidentally, I just got a knock-off Soda Stream from Phillips. It's over $150 cheaper and works 2x-3x times better. I wanted to build something similar for a homemade soda bar concept, and discovered how truly cheap it can be to make soda and carbonated water at home. I was shocked at what a simple concept it is, and how much of a profit these sodas water companies make. Phillips even charging $50 for their system is a total rip-off.
Truthfully, I think the increase in quality in the Phillips machine is due to fewer parts is an "exception that proves the rule" as these in-bottle carbonators seem to work better with fewer parts. It's just a pressure hose connected to a co2 tank. Literally, all of $6 if you were to build one yourself from parts on Amazon (or $3 if you got he Alibaba route)
I truly believe that the fewer parts the better in any DIY or commercial product due to the less chance of a failure in a part if there are fewer parts. This works fantastically for the "lower quality" producing companies, like Phillips.
My inventive and engineering entrepreneur friends and I call this "fewer parts the better" concept, a "Murphy's law compensator" as the fewer parts there are, the fewer parts that can statistically "go wrong"