It's expensive to go with even UPS since it ships as an oversized box. To get one of the stock ones I have shipped from NY to here was close to $100, or maybe a few dollars more. It was a couple years ago and the cost has probably gone up by now.
If they are going to use it to make a custom exhaust, cutting it in half between the SET and catalytic converter would let it ship cheaper. I had another shipped that I just wanted the head pipes and chrome covers and it was shipped for around $40 from Florida.
I don't know if they still do it or not, but Greyhound bus lines used to be a cheap way to ship. You need to drop it off at a terminal and it needs to be delivered to one.
Check on UPS's website and see what their description of an oversized box is. It may be if you removed the head pipes, chrome shields, and upper exhaust you could ship it in a smaller box. Or maybe even two boxes to get away from the oversized box charge. The one that I had cut up was shipped that way, the chrome in one box and the exhaust parts in another.
I think oversize goes by both weight and dimensions of the box, so it may not help taking it apart if you still go in one box.