Is it permissible for me to keep the remaining amount after repairing the car for half the estimated cost?

Compensation for financial damages is based on equivalence, by returning an equivalent item or paying its value. In this case, the compensation is estimated by the car's price before and after the damage, and the difference between the two prices is the due compensation. If the amount paid is equal to or less than the difference, then the remaining amount after repair is your right. If it exceeds the difference, the excess must be returned to its owner unless he agrees otherwise. The difference must be estimated by experts.