Oh, the obvious money saver with SS is that it can be finished naked. If you are coating it regardless then 4130 makes more sense.

I think this guy does SS racks. It is easy to copy the generalities of an SS rack, because there aren't many tubing options, so you pretty much know what it is about. One way to look at it very generally is that boring SS is not even up to regular structural steel numbers. So if you see someone's SS rack, and it seems to be 3/8", then it is probably 1/16" wall and if it was 4130 it could probably be 1/32 wall for the same design.