To estimate the price of the 2015 Mercedes GL500 V8 4.7L Twin Turbo Standard with 87000 km mileage, I first considered the selling price of a similar car: a 2015 Mercedes GL500 V8 4.6L with 96000 km sold for SAR 135000 in December 2023. Given the similar condition and specs, this provides a strong reference point. Next, I reviewed the listed prices of similar cars. The closest match is a 2015 Mercedes GL500 V8 4.7L Twin Turbo with 87000 km listed for SAR 130000. Other listings include a 2015 model with 106000 km for SAR 145000, and another with 106670 km for SAR 128000. Considering the mileage and condition, the listed prices range from SAR 95000 to SAR 145000, with most relevant listings around SAR 130000. Given the selling price and the listed prices, I estimate the market price to be slightly lower than the highest listed price but higher than the lowest, reflecting the car's good condition and relatively low mileage.