Depends on your weight and the materials cost when you get the work done. I'd suggest contacting David for a quote.
I will say that it cost me less, including shipping, than a graves exhaust. It also provides a lot more fun than the extra noise would have :)
I'm loving this suspension. Even on the cheap shinko 705s it sticks better than any bike I've ever owned and is incredibly stable even in rough corners and over expansion joints.
I would consider this suspension safety equipment if you ride in an area with rough roads, it's easier to justify to the wife that way, and it's true.