It depends on the grade of stainless. 300 series stainless has nickel and chromium content and is non magnetic. 400 series stainless has just chromium and is magnetic. So it really depends on the grade. I am not familiar with what is used in exhaust systems, I am sure someone else will chime in. Here is a link with some FAQ's about stainless steel:
http://www.ssina.com/faq/index.html A little noodling around on the web came up with 400 grade stainless being used in a lot of stainless systems, with the 304 stainless beign a "premium" exhaust. One site showed the 304 stainless exhaust for a Silverado at about $800, plus shipping not including labor. but cliamed a 1.0 million mile warranty.
Mike
