Here's a quick how to build a dual exhaust for 75 dollars not including muffler price. I don't quite remember the exact prices but off the top of my head it was something like this
4 45 degree bends from autozone = 32 dollars
2 pieces of 2 1/2 straight pipe = 20 dollars
2 2 1/2 exhaust flanges = 15 dollars
2 2 1/2 couplers = 8 dollars