Curious, why not just buy a tank of compressed nitrogen for that matter? What are the cost differences?
Because Nitrogen cannot be stored as a liquid under pressure at "normal" temperatures, with normal being temperatures that humans live at. You'd get a lot less volume of gas with a tank of nitrogen than a comparable tank of CO2 because the CO2 liquefies under pressure. Price difference? I don't know, It is probably insignificant, but you'd need a much larger tank to get an equivalent volume of gas.