A first-time Aldi shopper was surprised when a large grocery trip began with an unexpected requirement: getting a shopping cart meant putting in a quarter. After arriving prepared to fill several carts, the shopper initially assumed Aldi was actually charging customers simply for using them.

The unusual system can certainly look like a fee if you’ve never encountered it before, but the quarter isn’t really a charge. Aldi uses a refundable cart-deposit system. A shopper inserts a quarter to unlock a cart from the row, uses it normally while shopping, and receives the same quarter back after returning and reconnecting the cart.

The idea is surprisingly simple. Because customers have a small incentive to return their own carts, fewer carts are left scattered around the parking lot. That reduces the amount of employee time needed to collect them and keeps carts organized near the store entrance.

For customers making particularly large grocery runs, each additional cart requires another quarter while it is being used. However, those quarters are returned when the carts are properly brought back, meaning someone using three carts isn’t ultimately paying 75 cents for the privilege of shopping with them.

So Aldi isn’t actually making customers pay to use its shopping carts. The quarter temporarily acts as a deposit designed to encourage shoppers to return what they use. What initially feels like an irritating extra charge turns out to be a simple system that costs the customer nothing as long as the cart is returned.