A marketplace where the hard part is knowing where every card is

The problem

Selling a valuable card yourself means photographing it, grading it, listing it, answering questions, shipping it and chasing payment. Collectors with hundreds of cards do not want to do that a hundred times.

The operator takes the whole job. The seller ships a box in and receives money later.

The constraint

Around five thousand cards a month move through this, the commission slides from fifteen per cent down to three depending on what a card fetches, and the actual sale happens on a third-party channel rather than in the product.

Every stage can also fail or reverse. A card can be rejected at intake, fail authentication, be relisted, be returned after sale, or be withdrawn by the seller before it goes live.

The decision

This is a state machine with a shop attached, not a shop. The thing the system must never be unsure about is where a specific physical card is and what has happened to it, because on the other end of that record is someone's property and someone else's money.

So the model is built around explicit states and permitted transitions rather than around listings, and the commission is derived from the sale price at payout rather than stored at intake, so a reprice cannot leave a stale rate behind.

The result

Live, with the operator reporting five thousand cards consigned a month and over five hundred thousand sold across fifteen years in the business.