Watching this as a child and eventually as an adult, I've put the collection of "stuff" on a 10 point scale. 1 being a pure minimalist and 10 being an extreme horder. We all fit somewhere on that scale. I'm probably a 3 or 4. My father is a 10. Understanding where you are on this scale is important to de-cluttering your life.
Sometimes value gets set by factors other than price. Value & price are not equally correlated. Value can be translated as functionality, prestige, vanity, security, companionship, etc. People get value of things beyond price and each person sees a different value for each product based on their psychological needs.
All PG seems to be saying is to question an objects value before you purchase it. Otherwise, you could end up with a house full of junk that you and no one else will ever use again. In other words...Question everything, including value.