Truth is 70% of every breath you take is nitrogen..it's the most common gas on planet earth.
It's inert/non-reactive properties make it perfect for many applications from welding to gas shocks..
It's the equipment needed to separate and compress that costs the money.
As you've found out there are those out there that charge a lot to recharge!!
Current toys..
1986 Honda 350X..trail bomb!
1985 Honda 250SX..my main mudder
1985 Honda 250ES..Back in Black Trike
Current non-trike toys:
1990 Honda TRX300FW
1995 Seadoo GTX
1998 Polaris Indy Lite 340(Nearly new looking)
1998 Polaris Touring 500
1998 Club Car (electric)