To be fair, the pair that I bought, way back when, were used when I got them. So it is possible that the packing in mine was shot. The Super Duke has 23,000 miles on it. I took me of the FMFs apart the other day to check the packing, on that motorcycle, because it was so loud. But it was stuffed full, and still looked like new. Both the Sato's and the FMF's are glorified straight pipes. Loud is just what they are.
$550 is a bit rich, maybe. But when was the last time you saw a set for sale? Those were The Can to have, 10 years ago. I used to have my buddy do a "fly by" on my bike, while I stood along side of the road because it sounded so good.