Wow the exact same thing happened to me pretty much, I have a 2007 model car, there was 8500qr riyals damage to it, after an accident that was a POLICE cars fault, and the insurance company wanted me to pay 50% of the spares.

My dad went down to the insurance company, asked for ONE piece of documentation that proved we had to pay it and they declined. After a while they tried to make a deal saying we could pay 30% and they would pay the rest. We said no, were paying nothing, to get rid of us they then said OK pay 50% of a new tyre (which still cost 850qr) and they will waive the rest of the fee, so we said OK.

Go down there, say you want some proof that you have to pay this amount, to show your lawyer, or else you arent going to pay a riyal, that's the only way out of this scam i'm afraid.