To estimate the price of the 2015 Mercedes GL500 V8 4.7L Twin Turbo with 135100 km mileage, I first looked at the selling price of a similar car with 96000 km mileage sold for SAR 135000 in December 2023. Given the higher mileage of the target car, I adjusted the price downwards. Next, I reviewed listed prices of similar cars: one with 110000 km listed for SAR 95000, another with 108000 km listed for SAR 103500, and another with 106670 km listed for SAR 128000. Considering the higher mileage of the target car, I further adjusted the price downwards. The listed prices of cars with higher mileage (e.g., 204000 km listed for SAR 72000) also influenced the downward adjustment. Taking into account the condition and specs, I arrived at a reasonable market price estimate.