That's pipe he's using , good thickness too, it is probally scrap pieces he gets from oil field operations or chemical plant construction. If so, you want see rust on it soon. Construction at the plants in the area is wide open these days. There are at least 5 major projects going on the Mobile river alone.
His welds leave a bit to be desired . The end seams look good but the spot welds are very rough. Almost looks like two different welders. I would expect he will clean them up before finishing.
I bet the 350 price is the table top version.
