Without reading through the entire thread, if you love cars then it's worth it. If we take the economics angle, why don't we all live in tiny apartments, drive tiny cars, eat only protein and nutritional products, and all wear the same mundane clothing?
It's simple, we are all individuals. Individuals like to express themselves in different ways. There are so many different ways for one to express their individuality. Clothes, jewelry, music, art, etc. Modding a car can be an art. It can also be a way to compete, show off, have fun, etc.
For someone like me, it is definitely worth it.