'Necessary' is a very small box in the context of life. 'Desirable' on the other hand covers a multitude of sins, many of which are conveniently shifted into the 'necessary' box to justify the expenditure. You only have to look at the vast amount spent on vanity and ego to see that. How much is spent on clothes that never get worn? How many people feel the need to be seen in a high end motor, and for how many is it necessary expenditure? For a few it will be a spacious car with seating at bum level for ease of access on account of physical issues, but for the vast majority it will be a case of 'because I can afford it', or 'look at me'. Once you have risen above the destitute, this blurring affects all levels of society, so I'm not sure the safe is any different.