Cost refers to the outgoing money that reduces my assets. Whatever you buy, enjoy, or make a purchase, this is a cost.
It's like an axis of evil that usually has to be controlled and reduced costs in household account books, but in fact, costs are not just bad guys because they contribute to improving the quality of life. Like the saying,'I want to live far away and make money', all of my assets have to be used in the end to meet my happiness.
What we need to care about is not that we don't just use it, but rather manage it so that we can feel the greatest happiness at a minimum cost.