Super low tech.
Have you tried turning off all electric appliances, lights, etc. and unplugging the ones with no on/off switches and observing the meter with no load?
If the meter is still going at a good clip then something is amiss. If the neighbors agree they may at that point start turning off their loads while observing the meter. After all their loads are off bring on your customers loads and observe any differences between the respective meters.
I don't know what kind of meter it is so I don't know how difficult it would be to observe disk rotation, flipping numbers etc., but for $200 a month that thing must fly.
