"even if it weighed 500 pounds, it would be a good trade off. "
Depends on what you're trying to accomplish. Adding 500 lbs. to the front end of the already nose-heavy Stangs isn't the best idea if you're into handling. That would shift even more weight off the rear wheels - not a good idea when you're bolting on even more HP and torque.
I too am surprised at the weight of some of the components. I would've guessed 50-75; 100+/- lbs. on the front end from the ProCharger - wow.