Just to prove your point I weighed one hedman husler 1 7/8 tube B/RB header I have , thick tube walls and flange , on my bathroom scale , me holding it it was about 14lbs .
Then I weighed the right side repop hemi exh manifold I have , 21 lbs with me holding it , alone it was about 20.8
I'm not seeing 4 to 1 .... and I imagine a TTi hemi header weighs more than the hedman husler ...