← Spark & Whetstone · What the Snack Machine Knows
A snack machine is a very small shop. Put in the numbers an operator knows and read the three that matter: what a sale leaves, how many sales pay the rent, and how much to stock when demand is a guess.
Cost, commission and fee are each a share of the same sale, so they add: at 50%, 15% and 7% the three take 72% and leave 28%. Markup divides the profit by the cost; margin divides the same profit by the price, so a 100% markup is a 50% margin. Break-even sales are the weekly fixed cost divided by what one sale leaves, rounded up.
The stock line uses the newsvendor rule. A missed sale costs the profit it would have made; a wasted item costs what it cost less any salvage. Stock enough to cover demand with probability (cost of a miss) ÷ (cost of a miss + cost of waste), taking every demand from low to high as equally likely. Cheaper waste means stock more.
The change line uses Spark & Anvil's money engine, copied here unchanged: the fewest US coins that make the change from $2.
Trade ranges operators report are roughly 45–55% cost of goods, 5–25% commission and 5–10% card fees; yours will differ. Nothing on this page is stored or sent, and none of it is advice about a real business.