I have a 2013 X5 diesel. Put about 50,000 miles on it now, closing in on 100,000 on the odometer. Great car, strong engine. It needed a pump for the DEF tank, and later it needed a DEF tank fluid sensor. Each repair was $400 or so at the dealership. Recently, the oil return line from the turbo was replaced for $600. The gas mileage is incredible for a luxury SUV.
It's not the least expensive car to run, but the torque is amazing and I've found it to be a great tow vehicle.