The cost of the skimmer is insignificant, but the labor to replace it adds friction and is going to reduce the number of active skimmers. To replace the removed skimmer will also expose the criminal to more risk of getting caught, especially if the police are aware of the removal and can set up a sting or something.

So while the economic ROI is so high the behavior will continue, it does slow them down.

Not a complete fix by any means, but adding friction to their criminal behavior.