I've been looking at prices to replace a modified, ie cut up exhaust system.
To replace it with new factory parts would run over $3000. for Ca spec exhaust.
Just something to think about when planning a mod job. If I was going to mod I'd remove the costly stuff and just build the replacements, the next owner might want the original quiet system.

 

I had mine built in sections. You can unbolt sections of mine and bolt the stock stuff right back in. Except for the Y pipes which is a **** design as it is. So the 4 rear muffler sections are removable. You can run the very rear. The mid rears. Or two on one side - one on the other - whatever combo you want. Sold it to my neighbor who said it was too loud - put the rear most mufflers on and then it was too quiet lol

 

exhaust parts in california wear exceptionally well, and as such the used market for them is VERY reasonable. You can buy a complete exhaust, cat-back, for a couple hundred dollars, sometimes less.

That said, It's cheaper to build a "quiet" performance system than to buy the OEM parts again.