Be prepared to spend that much if your gonna go with a high performance exhaust system like MAC or
Magnaflow. I personally just wanted the look and sound and of course did not have 500 to 700 to drop into a exhaust. So I pretty much scanned message board after message board and found a GT Take Off from the headers back in excellent shape that I picked up for $50 locally. Then one of my neighboors notices I have a Mustang now and gives me his old 2002 GT Stock Exhaust he had laying in his garage for free. I sold that 2002 GT stock exhaust to pay for the install for the original GT exhaust system I picked up for $50
I ended up going to a custom exhaust shop nearby and the dude wanted $400 to install the GT Take off exhaust! I ran out of there laughing and asked around to find a "hole in the wall" muffler shop in a small town nearby to me. They installed the GT Take Off Exhaust for $75 which included any hangers that had to be made and modifications.
Hope that helps paint a picture on cost ...