Hmm. I don't think it's quite that simple, since it's Ryanair headquarters who are taking in the money, not a 3rd party. It's a charge for carrying the bags on the Ryanair plane, not for ground handling.
IMHO, regardless of who runs the scales, or whether or not this is actually happening, Ryanair need to keep the scales accurate and fair, and be seen doing so. Blaming a 3rd party is not going to cut it when they may be making money off the back of any errors.