There's a fastfood chain in Poland named North Fish, which serves relatively expensive fish burgers etc., but at the same time offers a 50% discount on everything during the last 30 minutes of their business day.

The lines are indeed short there, but I only discovered this discount scheme by accident - they don't advertise it too heavily.

The food is average for the price and they're always right next to other options which leads me to believe that it's the short lines that are their product.