The cost never shows up at the start. A model that stores an address as one line of text works fine until somebody asks for every customer in Pune. A model with no relationship between an order and the items in it works until you need to change one item.
Sketching it is not really technical work. It is naming the nouns your business already uses and deciding which of them can exist without the others. The useful version of that conversation is with the person who does the job, not the person who will write the code.
Updated September 2026