From what I understand the Pacesetters are made out of mild steel. Theres also the S&S Autocrome headers that supposedly have a lot better fit than the pacesetters but they are made of mild steel also.
My quick google search of "mild steel" tells me that it is basically cheap steel with a low carbon content. It also rusts.
I dunno if I would put something as big as headers on my car with steel of such bad quality and not worry about it. But the SLP and TOG headers are twice the price, but thats probably becuase they are twice as better quality.