I looked up fabric weights - the lightest 200 d. coated oxford nylon is 4-5 oz/sq ft. I measured my legs and I am short and small - and figured it would take 2 yards of material. So without the rubberized foot, this would be 8-10 oz. You can buy rubberized coating solutions - painting this on the foot would probably add 1-2 oz. The rubberized sole is to prevent slipping, not to waterproof. So a small pair of waders could be 9.6 oz. However, this is the lightest material and I really wonder how long they would last. I think the first sharp rock you stepped on you could spring a leak.

$60 is a fairly high price for an item that may not last.

Another major concern I would have is the safety of using a "wader" to cross seriously difficult streams. Fine if you are crossing knee-deep water or less. If you accidently step into a deep hole and the waders fill, you could be in trouble. If filled with water you may be unable to move due to the weight of the water inside the waders.

I see that these waders do have an application, and theoretically could be the advertized weight but be careful to evaluate how you will use them.