You are an optimist Robert ... and that's good , if i sold products like that i would lose custom , this i know for sure , the answer to why it's a gimmick is in your own statement,
Systems that cost 300$ and 20$ a month are expensive because it's the only way to do it,
that product won't even produce the amount of co2 that will be in your rooms atmosphere anyway, also , there is no way of testing it , the experiment i used on the co2 tablets won't work because the meter won't pick up on anything because of the way they are claiming it works and the action it uses,
The only way you could run a successful experiment would be to run plants with and plants without and then other circumstances could and would give you an inaccurate result.
If they really have come up with an amazing new product then answer me this , why is it so cheap and i notice there is no patent on it ?