With the Etude House membership card you can take advantage of their random sales.
Etude house sometimes sets up a large 'up to 50% off' poster outside their store, meaning that a majority of their products are on sale. Inside you'll see sections and shelves marked with stickers on them tellng you how much % is being taken off. The 20% and 30% stickers are more frequently seen.
Of course, this discount sale is only available for membership card owners. Visitors without a Korean ID card or ARC unfortunately cannot set up a membership account.
This membership card is going to be like the Body Shop card for me, fantastic but lethal to my bank account.