Jon: My concern is quality of weld not cost of gas. A tank lasts me 1-2 months now. So it is not a big cost compared to the benefits of the wire welder.
An example of my concerns. Today I had to do some welding on a bale trailer. Just some flat irons I added to keep the bales form sliding off sideways. They are light flat iron deliberately. They are always getting hit accidental. This way they give rather than some thing major. Half way through the repair I had to switch wire when I ran out. When I started to weld after that I got worm holes in the beads. Same steel, ground clean, inside so zero wind. The wire brand was different but the same size and rating. So what changed??? Even more puzzling to me is that after a few welds it quit doing it.