To estimate the price of the 2014 GMC Sierra SLE V8 5.3L V8 AT4 Regular Cab (AWD) with 255000 km mileage and average condition, I started with the new car prices of similar variants. The 2025 GMC Sierra 5.3L V8 AT4 Crew Cab (AWD) is priced at SAR 255760, the SLT Crew Cab (AWD) at SAR 201870, and the Elevation Regular Cab (AWD) at SAR 214206. Since the target car is a 2014 model, I applied a 10% annual depreciation over 10 years. The AT4 variant is the closest match, so I used its price. The depreciation calculation is: 255760 * (0.9^10) = 90660. Considering the high mileage and average condition, I further reduced the price by approximately 20%, resulting in an estimated value.