I think it depends on what the canister is made of. Some are steel and some are aluminum. But you probably know this if you have already read every thread here on the topic. The steel ones today have very little scrap value. The aluminum ones, I would guess, would be worth a couple bucks a piece AFTER they are broken down and most likely cut in half so the yard will even take them. Some have brass handles and tubing. It would take an awful lot of those to really add up to anything worthwhile though.