I don't think you can get a new pressurized CO2 system for $100, but if you watch the for sale areas of as many forums as you can, and jump real quick when someone offers one for sale, you can get a used system for about that much. My Milwaukee regulator cost me about $75 as I recall, and the CO2 bottle was around $40 or so (on ebay), then another $15 to fill the CO2 bottle. It is hard to get a lot cheaper than that. I found that buying a used regulator on ebay seems much cheaper, but by the time I bought a needle valve and all of the various adapter fittings needed I spent much more than the Milwaukee regulator cost, and still didn't have a solenoid. (If you haven't figured it out yet, I tried to go cheap, but ended up paying double cost by buying lots of stuff I didn't use before buying the Milwaukee unit.)