It cost me $400. That includes two Flowmaster 40 Series mufflers, all the necessary pipes and clamps, and two stainless steel exhaust tips, plus labor.
It sounds really good. Sounds like a V8 Mustang GT, and it's not too loud inside, just a low hum. He split the pipe, wrapped one around each side, and then put the Flowmasters right at the rear with some nice tips. Also, he used 2.25" pipe, you don't need any bigger with duals, plus, it'll fit beter. I probably added about 8 HP doing this.