Hmmm, I thought it was 2€ per day, but looking at their site says different:
FOR ONLY € 4,00 PER DAY (*), YOU CAN COVER ANY DAMAGE CAUSED TO WHEELS, GLASS AND CLUTCH (**)
* minimum amount € 20,00 and maximum € 50,00 per rental contract
** a deposit of € 300,00 is obligatory, in case you do not wish to acquire this insurance
I am collecting a car tomorrow evening and I usually pay for the extra as they are usually short rentals, will let you know.
Mark