This is 2005-2009 Era and was on my 2006 Spec B:
I have one single muffler in almost perfect shape from the SPT set. My car was rear-ended on the right side so I have the left-side in-tact and ready for someone who needs it. I had less than a year on it and probably less than 10K miles on it.
It weighs about 30lbs I guess so shipping might be a bit high. I am not sure how much this is worth, the whole SPT system was about $1200 and this is say 30% of that system, so I would guess somewhere around there or less?