Must be made out of Platinum....I always get my systems bent by a good friend who buys me straight lengths of stainless and bends to my design. I always use the Turbo Corvair mufflers from the 60's Chevy Monza Turbo Corvair, reputed to be one of the lowest back pressure mufflers GM made. 

I see the mufflers for less than $30 at the stateside big box auto suppliers and Summit sells stainless 2.25 " x 4 feet for $30. So $60 on mufflers and another $120 or so on pipe throw in clamps and bending, gotta be under $400.

My last 3 sets were 650 at trade price