You probably wouldn't demand a do-over on the scale at the doctor's office, but an inaccurate weigh-in there wouldn't cost you a dime. When it comes to weighing your luggage, however, an airport scale that's off can be costly. It's times like these when requesting a re-do makes sense for your bottom line.
Budget Travel comes right out and says that airport scales often lie. Scales at several major airports aren't properly calibrated, which means passengers are paying hefty fees for overweight luggage when their bags aren't actually too heavy. Brandon Macsata of the Association For Airline Passenger Rights recommends that passengers weigh their bags at home first; if the airport scale seems off, ask that your bags be weighed on a different scale.