Sorry but this was stupid to me. Most of the weighing systems out there are going to use the bell alarm to actuate a pneumatic arm to push the offending box off

Sorry but this was stupid to me. Most of the weighing systems out there are going to use the bell alarm to actuate a pneumatic arm to push the offending box off the line to a reject pile. What you actually will find is they will have an over and under bin so you can find out if you are over or under filling. It is a requirement by law that they weigh the product on a "legal for trade" scale if they are claiming it contains a certain amount. The company would already have the weighing equipment in place, maybe farther up the line where the tubes are filled. They would simply have to move them down to the end of the line and change the weight range to add in the weight of a box and any other things added to the box and toothpaste tube. I get that it is a thought exercise but wanted to add my 2 cents.