Funny, when I was a student and worked at a hardware store that was almost the exact example they gave as encouragement. You want the customer to trust you and the store and so most of the time their projects start with a box of nails. Do they need the tinpenny, concrete, roofing, anchor nails, or tacks? Most people who know what nails they need don't bother you. But the guy/girl starting on their first renovation or garden are practically begging you to take their money. Personally, when I step foot into a hardware store it's a given that I'm leaving with $100 worth of stuff.

Now a better example would be consumer electronics. It's expensive, most people don't know what they really want they read some review in engadget, and the margins on the name brand stuff is extremely low ($5-10, on Sony TVs for example).