Just a further note on refills, I recently purchased a Tig welder, c/w a small argon bottle. I took the cylinder to Air Liquid in Grande Prairie, and they did an exchange for the price of gas. No contract. He said it was a Prax Air cylinder and they have an agreement to exchange hobby size cylinders between Prax Air and Air Liquid.
I've been leasing bottles from Air Liquide for close to 30 years. Every year the price was always climbing until i was paying over $130 per year per bottle. I went in to complain and they offered me a 3 year lease on 16 and 22 size bottles (100 and 120 cf) for $120. For $40 per year it almost seems reasonable.