90% of my driving is "in-town" in my 2013 X5 50i with M Sport and M Performance. To date I am getting on average 12.9 mpg. As you pointed out, anytime I am on the highway at a consistent 70 - 80 mph, I am getting around 24 mpg. For me, the growl of the engine and the pin my backside in the seat feel that I get is worth the reduction of mpg.
2013 X5 50i - Space Gray - Cinnamon Brown - Dark Bamboo - M Sport - M Performance - Premium - Premium Sound - Tech - Adaptive Drive - BMW Apps - 3rd Row