Loss leaders is an item sold at or near cost for the store, that they put out to lure you in.They want you to do the rest of your grocery shopping while you’re there. So you need to be disciplined and not be sucked into the loss leader trap.
Milk is a popular loss leader item and that is why you find it in the back of the store. The grocery store wants you to walk as far as possible to come in for the loss leader item and then buy some more groceries while you are there. Many of the items my wife and I buy when we are at the supermarket are loss leaders. We will stock up on as much of it as the store will allow and then buy the necessary grocery items to get us through the week. Coupons, loss leaders and the like save my wife a lot of money on groceries.
Read the ads carefully, to make sure there are no requirements attached to the loss leader.