You have good reason to be peeved. But, think of it this way: (first figure the actual distance between these two locations in question) If the trip was 210 miles, and the car departed the home dealership with 3 miles on the clock, it is safe to assume the car has only had 1 driver. And that's only 1 chance of a possible A-hole driver. If you bought a car with 40 miles, you wouldn't have a suspicion and there is a possibility of 5+ possible A-hole drivers on test drives (assuming ~<7 miles per test drive). Being a luxury brand, we can assume fewer A-hole drivers would find themselves behind the wheel, but it certainly is sporty enough to beg for a hammering.
I think I'd rather buy a new car with 200 highway miles than 40 test drive miles.
Depending on where you are in the process, you could have a nice bargaining tool to your advantage. Raise a stink and demand retribution. Ask for an oil change (probably should watch them do it). Depending on how nice they are and how bad they feel, they could through in a service package, extended warranty, or accessories like said above. Probably a good time to check out the accessory catalog.
