There's also the annoying other side where Amazon shipped a clearly underweight package but refuses to acknowledge their own equipment's measurement for a return. The person bought a 7-8 pound graphics card and the package only weighed a little over 1 pound according to the package's own shipment info. Amazon is still giving the guy the run around demanding police reports etc when it clearly left the depot without the gpu.

Does depend on how heavily the item was… “Tested” before it was returned.

Many products will also have inconsistent weight, not only between units (not everything is made to NASA specs, and anything handmade or harvested will have huge variations) but also after shipping (labels on box, seal tape or cellophane removed, cardboard absorbing moisture, …).