cheap...drives a 40K plus vehicle and don't want to spend 500 bucks.
Now in a serious note...
I don't think they (most muffler shops) have the quality materials, quality welders and the skills to make something nice, clean and neat. Now if you want something far from neat, clean, symmetrical and so on then any "butcher shop" will gladly make one for you.
From previous experiences, any muffler shop in town is not capable of doing it at least with the amount of care and detail that our vehicles deserve.
Unless you want something like this:
bad repair1.jpg
badrepair2.jpg