Washing a car can be therapeutic, but it also depends if you are washing your daily driver or a garage queen. IN either case there are some great You Tube videos on how to correctly wash a car without causing scratches or water spots.
IN the past couple of years I've become a big fan of using a pressure washer along with foam guns for both washing and waxing the daily drivers. The garage queens a re a bit different as while they do not see any weather, washing is a much more detailed process along with clay baring and polishing with a high end orbital happens at least one a year.
Regarding the previous depreciation discussion. BMW's are OK cars but no longer the best in class. Also, BMW is now a volume producers and especially the 3 series in now a "belly Button car".... everyone has one.