I bend tubes for a living...most of it is 304 stainless on 1 to 1 radius up to 7" in diameter. It isn't easy and I completely understand why headers cost what they do.Especially ones pieced together from individual bends...we use CNC benders and do the bends all out of one piece of tube unless the straight lengths are so short that it isn't possible, in which case we compound bend them. A few we cut and weld but not that many.