Where do you get 1/4 wall perforated tube? It sounds expensive compared to regular box tube straight from the mill. And each bolted connection made with graded

Where do you get 1/4 wall perforated tube? It sounds expensive compared to regular box tube straight from the mill. And each bolted connection made with graded fasteners is going to cost several dollars, which adds up very quickly. A circular saw, a mag drill, and a stick welder could take you a long way on a project like this, and you could use regular steel plate, tube, angle bars, etc. I think a lot of cost and weight is being sacrificed in the name of "modularity", for questionable benefit.