We could have used a pay-per bag scales at LGW 6 years ago. We were flying long haul and had just one large suitcase between the 2 of us and well under the 46 kg limit.
As we queued we saw a sign that said make bag limited 32 kg.
Our queue was so long that it snaked passed an empty checkin desk. Quick detour and it weighed in at 31.5 kg.
How much better if there had been scales readily available.