Here’s an ethics question: at what point in your retail experience do you call attention to being undercharged (or getting too much change, which is the same thing)? If you are standing right at the cash register and get a nickel too much, you might give it back. But if you don’t realize the error until you get all the way home, unless your name is Abe and you have a stovepipe hat, you probably won’t worry about it.

What if the error is $20? Does that make a difference in your answer? I once got undercharged $20, if I recall the figure correctly, and I took it back to the store the next day, mainly because I didn’t want the checkout person to get in trouble.

How about $40?

Yesterday, I transferred a prescription to a local grocery store which has a pharmacy. I was attracted by the fact that this grocery chain (like one of its competitors, a big discount store chain) is now offering some generic prescriptions for $4. That’s less per month than I’m currently paying for my mail-order prescription.

My mail-order prescription had been for a 90-day supply, which my insurance company allowed because they are affiliated with the mail-order supplier. I knew that the grocery would only be able to give me a 30-day supply.

But it turns out that this particular drug is so inexpensive that they told me I could pay cash, bypassing my insurance company, and get a 90-day supply for the same $4 per month, a total of $12. It sounded good to me.

Here’s where things got interesting. I didn’t know about it in advance, but this grocery chain also offers an incentive for people who transfer their prescriptions: $20 in free groceries for each prescription transferred to the store from some other pharmacy.

When the woman in pharmacy was ringing up my purchase, she told me about this, and I was pleased. But then she said something along the lines of, “well, you got a three-month supply, so I should probably count this three times.” So she put a $60 credit on my grocery card.

I am almost certain that she interpreted the promotion wrong. I was only transferring one prescription, regardless of how many months’ supply. But it was her conscious decision, not mine, and it would have been kind of arrogant for me to argue with her about her own store’s policies. It wasn’t the same thing as her accidentally handing me the wrong denomination of bill.

So I shrugged and got over it. And today, after I got off work, I went and bought groceries.

Was I wrong?