To estimate the price of the 2012 GMC Acadia V6 3.6L AT4 (AWD) (Mid) with 276000 km mileage and average condition, I considered several data points. First, I looked at the selling prices of similar cars. The closest match in terms of variant and condition is the 2013 GMC Acadia V6 3.6L AT4 (AWD) (Mid) with 153000 km sold for 20500 SAR on 2024-05-06. Given the higher mileage of the target car, I adjusted the price downwards. Other relevant data points include a 2012 GMC Acadia V6 3.6L SLT2 (AWD) (Mid+) with 185000 km sold for 15000 SAR on 2024-05-13, and a 2012 GMC Acadia V6 3.6L SLT2 (AWD) (Mid+) with 177775 km sold for 25000 SAR on 2024-01-03. Considering the higher mileage and average condition, I further adjusted the price. Additionally, the listed prices for similar cars with the same variant and mileage range from 19500 to 26500 SAR, which supports the downward adjustment. Taking all these factors into account, I arrived at the final estimate.