Green Dragon -

I checked out that site, and they do have good prices on a few of those items. For instance, I can get a Beck/Arnley Timing Belt and Tensioner for $198 shipped (while similar parts at Schucks would cost me about $30 more).

However, I'm still a little confused about that TB Tensioner. Obviously it's a part that keeps tension on the timing belt, so I'm assuming it's a good thing to replace, but why the heck is it so expensive? Can someone explain to me what it is and why it costs so darn much?