The trick to inexpensive McDonalds is to use the app
$5 Spicy Deluxe Crispy Chicken Sandwich meals
The app is a LOT cheaper than the original pricing. The deals are also pretty consistent. They were giving free Large fries until I took advantage of the deal x3 without getting anything else and now I no longer get that deal...
Starbucks tries to gamify buying certain items or repeat visits for extra stars.
How else would they offer fries for $1? Cheap transportation? lol. I built it, I know.
Someone else in this comment section said it, but I think it's more about a way to do price discrimination. They can still sell at a lower margin to more price sensitive customers through the app, and get higher profit from people who don't care about the higher prices.