I am trying to think how you could even make a counterfeit CO2 cartridge. The CO2 is liquid and the pressure is its vapor pressure so you can't skimp on the steel. I guess you could make it out of more and worse steel and put in less CO2, but does that actually save you anything? Surely the biggest cost here is distribution. And it wouldn't interface with all the things that might use it. Before that, you'd have to invent and make the machine that makes the counterfeit cartridges.