How much to spend on oneself? As much as is needed to extract the maximum work and value from oneself. There might be times when you need to spend on servicing the car. Fine, that much expense is needed. Otherwise, the car will not be helpful anymore. I need to take it to the destination.

But to keep decorating the car with accessories—having bejeweled cars, diamond-studded headlights, doorknobs made of platinum…

The fellow sold the tires to get the platinum doorknobs! That’s the story of our lives, no?