Just a different perspective, but maybe you are paying for all the R&D for companies like HKS, Fujitsubo, Blitz, Weldina etc that goes into designing an exhaust that has the right sound, right volume, right flow characteristics and certain rpm.... and bolts straight on.
Just a thought... I mean can you imagine these copy companies trying to design something instead of copying? Do you think they would/could come out with a similar high quality unit?