Their package weight if I recall correctly was 7lbs together not each. Putting 3.5 lbs on each wheel. I saw no difference either, and their stability made them well worth the investment.
Edit, also the spacers cause the rub on the body mount in the rear of the wheel wheel(only with 285s for me though). While it does push the wheels out, if you lock the wheels without them, you can see where the tire turns inside of the body mount. When you go up to 285s and it turns the wheel in the path of the body mount. While not enough to hang up or act as a stop, it still makes a pretty nasty noise that will scare the s*** outta you if your not ready for it. lol