It applies to most DIY projects of any scope.
Changing the oil in my car after 3,000 miles instead of buying a new car. Win/win.
Replacing the screen on my front door myself vs hiring someone to do it or buying a new door saves me money and is far more satisfying. Win/win.
Steeping actual tea instead of using the stupid Keurig at the office is tastier and cheaper. Win/win.
Cooking up dinner myself is tastier, cheaper, more convenient, and healthier than dragging my ass to a restaurant. Win/win/win/win.
Feeding our dogs a species-appropriate raw diet instead of kibble is cheaper, far healthier for the dogs, tastier and more mentally stimulating for the dogs, and makes the dogs produce far smaller poop in our back yard that disintegrates/decomposes within days. Win/win/win/win/win.