At your local exhaust shop probably none. At HKS however quite bit I would think.
These are the same parts they would have on their own HKS car, probably also the same parts on the cars they sponsor. When the main goal is to get exhaust out of the engine you don't want unnecessary bends, overly large bends or poor welds creating turbulence.
This is something I would think big performance part companies would be able to repeatedly test until satisfactory results are achieved and then have a computer recreate that perfectly every time after.
Then again I could be wrong and they could outsource them from China