David Smith /

Almost all retailers constantly are trying to think up ways to get more people into their stores. And it gets harder and harder to come up with new ploys.

But occasionally they come up with an offer so good that it scares them. So the retailer starts adding conditions to make the offer less costly to the store.

Listen to this offer from Staples: a coupon worth twenty dollars off an in-store purchase of twenty dollars or more. One day only at the Memphis store only.