The catalogue and the cart are the visible part. The expensive part is what happens when payment fails, when stock runs out mid order, when a delivery zone is not served, and when an order needs a refund. A store is not a brochure with a buy button.
That is why an online store is priced above a business site on our pricing page, and why a competitor's online store priced the same as their brochure site is a brochure with a buy button.
The store tier on our pricing page includes catalogue, variants, stock, MoMo and card payment, failure handling, order alerts and admin training, because those are what make it a store.