Even if you only order from Amazon, your experience also depends a lot on how Amazon have handled returns. I’ve had Amazon ship out returns they’ve processed where the item was supposed to weigh about 10kg, because it was a pack of 60, but weighed little more than the box because somebody kept 59 and returned just one. If they’d done a simple weight check on shipping then the whole thing could have been prevented.

This is a problem that bricks and mortar stores are also faced with – especially when the box has been resealed in a way that makes it look like it was never opened.