Why that ‘free’ supermarket turkey isn’t really free

As we get closer to Thanksgiving, Americans naturally think a lot about turkey, as in how to prepare it or what to serve alongside it.

But here’s something they may obsess about even more: free turkey.

This is the time of year when many food retailers roll out offers for consumers to score a bird at no cost, provided of course they spend a certain amount. The deals vary in their terms: BJ’s BJ, -3.23%, the wholesale club, requires a $100 purchase, while ShopRite, the supermarket chain, sets the bar at $400, but also lets...