Part of the reason why Aldi can offer such low prices is their no frills approach to the 'retail operations' side of their business, which boils down to 3 main elements...
- Limited choice in their product range (You'll never find more than 2 types of any product on their shelves - you will rarely find the big brands advertising on prime time TV)
- Basic shelving / merchandising layout (products are generally stacked tight in bins, on palettes, etc., with a neon A4 page above showing the price)
- Speedy checkout (Aldi actually train their staff to scan a customer's goods as quickly as possible; they also have much smaller packing areas than other shops, and less 'exit space' for you to actually leave the shop post-checkout. They want you to pay and leave asap!)
This 'Ryanair style' approach to retail doesn't work for everyone, but it keeps Aldi's prices low!