Same reason people will pay $800 for a bolt-ons. People will pay it. Always seemed a little steep for two little chunks of metal IMO.
Because of the stock header pipe,one side will be higher(brake side) then the other. Would think for that amount of $$ they put a bend in the one side to make them even from looking at them from behind. I may be wrong on this,but last time I looked into them it was like that. There is certainly a member here who has them that will probably chime in to confirm or deny this. Heard they sound sweet too.
Have seen people(member) put one voodoo stubby on after market headers with knowing the outlet diameter of the pipe. Via phone call to distributor.
Don't buy from Lord Humongous... He's a tool N they look like mortified exhaust tips you get from auto parts store. Another member here sells the Auto chrome tip mod for about $70ish on Ebay.
Good Luck!