When I use the CO/2 for the pushing power, I just set the output presure of the CO/2 to approx 20 PSI. Ya just have to be on the ball and realize that air compresses so even after the valve is shut off, it will still keep pushing untill the dump valve is opened to release the preasure.
After stuffin about 25 pounds of beef snack, I could not tell from reading the regulator gause that I had even used any of the CO/2 in the tank. I know I did, but my point is, from this very first use, I'm confident that the tank of CO/2 will last for a heck of a lot of stuffing.
I'm told the refill will be about $27.00 when I need a refill. Here in Washington at my local welding supply store, the tank, regulator and contents cost me $237.00 give or take a few cents.