I have this thing about the 3 German luxury/sport makes. This theory is only for guys and is quite generalized also applies to new cars and not second hand.
BMW = Young men who landed arse first into a well paying job and want something that looks mean and goes like the clappers. Also wears sporty Oakleys and can only afford the car from the high car allowance.
Audi = middle aged/well established businessmen who have a family and usually buy sports models for the midlife crisis. Practical, reliable and fast.
Mercedes = Old farts who refuse to drive faster than 10km under the speed limit. Life for them has all come up to the point were he blows all his investments on a 2 door AMG but heart/reaction speed cannot keep up with the car.