Source: Science Explains Why You Always Buy Too Much Stuff at Costco.People don’t shop rationally. They make decisions based on an “emotional tug of war” between the pleasure and pain sensing parts of their brain.
But it’s not enough to just excite the NAcc (pleasure): retailers must also inhibit the insula (pain). This is where Costco really excels. When consumers are repeatedly assured that low prices are “guaranteed,” or told that a certain item is on sale, the insula stops worrying so much about the price tag. In fact, researchers have found that even when a store puts a promotional sticker next to the price tag⎯something like “Bargain Buy!” or “Hot Deal!”⎯but doesn’t actually reduce the price, sales of the item will still dramatically increase. These retail tactics lull our brain into buying more things, since our normal response to price tags is pacified.