$5 goodwill file cabinet, some blue paint, and a new MM 211 which I absolutely love, for what I use it for.
Total investment in the cart, $5. I had the wheels left over from a lawn mower that I scrapped. I had some John Deere wheels the same size but the yellow really didn't go well with the blue cart. I wanted the cart to be blue, I originally was going to order the correct Miller paint but it's not cheap. I had the blue paint at home already so I just used it, even though it doesn't quite match. The caster wheels came in the cart.
The spool gun in it's case fits in the bottom drawer with the helmet. Top drawer has the bottle cap, wire, and a small tackle box with some tips, wrench, etc in it.
I did build the frame out of tubing, it's all throw away stuff from work. Yamaha crates...actually the racks that they used to ship the Vikings on. They'd ship them 2 up, one on top level and one underneath. Lots of 1 7/8 .070" wall square tubing and then 4 round bars for supports, they're like 1" round and .187" thick.