COGS / production per unit is the critical omission: your list captured every fee layered on the sale but not the cost of the plate itself, which is the largest variable cost for a print-on-demand product. Selling price & units per order supply the revenue side — nothing computes without them. Refund rate (not just admin) drives the real return cost: lost COGS + a metal poster you usually can't resell dwarfs the admin fee. Affiliate attribution mix stops the model overstating commission by applying it to organic/paid orders that never triggered a payout. Packaging, seller-funded discounts, and sample amortization round out a true contribution figure. Not modelled here but worth a note for the full plan: VAT/sales-tax treatment on cross-border orders (usually pass-through but affects landed price competitiveness), chargeback/fraud provision, and customer LTV — this model is first-order contribution, and repeat-purchase economics will look materially better.