Assessment Disinterest

I took my vehicle to CK Coachworks for assessment of the damage to my vehicle. Yushri Bucks looked over my vehicle in the street for a whole 5 mins took lots of pictures and seemed more interested in how much tread I had on my tyres. He sent a quote through to Discovery Insure for 8,400 rand. I took my vehicle to two other body repairers and both of them pointed out that the shock absorber behind the bumper had popped and this alone cost R5,500. When I called the assessor he said that once the vehicle is stripped if there are any extra costs Discovery must be informed and they will sanction additional expenditure but why can the job be done correctly first time and get a true cost. i phoned their head office in Bedfordview and they said they stand by their assessors value