When things cost less than they should, what they are selling you isn’t their product. You are their product for someone else.
Not necessarily true. Sometimes it’s a loss leader. Sometimes it’s making room by getting the product out of the way. If Walmart buys 1000 of something, and recoups their money by selling 900 of them, the rest is profit. They’ve partially saturated their market, but they can roll back prices...a little, then a lot....to move the merchandise. All profit. If the last 5% are sold at a slight loss, they’ve still made money.