There have been numerous reports here on FT that European agencies are much stricter than U.S. ones about damage -- even cosmetic damage -- to wheels. That's unfortunate, but certainly not a scam -- unless the agency knew that the damage was pre-existing when they rented the car, and still tried to charge the next renter for it.

It's been my experience that a rental-car agency has no burden to prove that damage on a returned vehicle is new; rather, it behooves the renter to carefully inspect the vehicle for damage before driving it away, and then having any pre-existing damage noted on the rental agreement or on a damage slip. (Whether Spanish law requires something different, I do not know.)

And a rental-car agency that collects money for damage that occurred while a vehicle was rented out has no obligation to repair the damage. They've been made whole by collecting the charge for the damage. They just can't charge the next renter for the same damage, but it's up to the next renter to spot the damage and have it documented before driving the vehicle away.