Standing in a Radio Shack yesterday, I watched a customer walk in with her new phone. With box. With receipt. She says, "This phone came without a power cord."
The clerk argued for a while.
The manager came over. He proclaimed it impossible that it was missing. He then offered, "as a one-time accomodation" to sell her a new power cord for half price.
First, why bother with the one-time nonsense? Do they keep a list? Does every Radio Shack in America now have this woman's picture in the back... "Don't sell her another power cord!"
But worse, why not just say, "Get out! We hate you! We don't trust you! We don't want your business!" Because that's what charging her $10 for a new cord was.
Either you're going to make someone happy or you're not. Doing the 'right' thing is irrelevant.
Here's the short version: If you try to teach a customer a lesson, you've just done two things:
a. failed at teaching a lesson
b. lost a customer