I love this specific promotion, and others similar to it. The basic idea is after ordering online, you’re prompted with an option to share the sweetgreen app with your friends and in the process earn both you and the people you share it with $3 to spend at Sweetgreen. Given that you just placed an order through the app, the promotion assumes you’re a fan of the service and that that $3 would be pretty valuable to you…and at the same time it’s an enticing offer to a friend. $3 is significantly less than the price of most items there though, so really you and your friend would be spending well over that amount, which is great for Sweetgreen in the short run — not to mention the long term benefits of getting new subscribers (I’m sure they’ve measured out the LTV of new customers who come as friends and the number comes out to something higher than $3).