Say that somehow a big-ticket item at your shop got marked down to something like 10, 15 percent of its true value. And say that somehow you didn't realize it until quite a few customers bought it.
Do you call the customers and demand they return the purchase, knowing they'll be furious and likely not come back? Or do you suck up the losses and keep the customer happy, and hopefully come back and tell all their friends?
This is what happened at Sears. The ipad2 got listed starting at $69, instead of its usual $499-$799, at their online store.