Kilt repair needs are highly variable. Especially with wide variances between homemade kilts by family members, and even professional kiltmakers have different styles from company to company.
So much like an auto-mechanic I can't give you an exact quote on an extensive repair until I see the kilt. Depending on what the needs are the repair can range from $20 to $250. Once you order this I will contact you to discuss the repair and the ballpark cost.