The price of a product on the market is the sum of the cost and profit. The cost of the 3D model is not zero. When the Seller creates a price for his model, he calculates the time for its creation, etc. It is not entirely correct to discard the abstract 30 or 50% of the cost. Perhaps it is more correct to form the price as a sum of a constant denoting cost and profit. And discount the percentage of the profit?