Build an independent basket-comparison service that calculates the expected checkout total for the same shopping list across nearby retailers and fulfillment methods. Start with receipt uploads, customer-submitted checkout screenshots, and manually maintained prices for a limited geographic area rather than attempting complete national coverage. Show substitutions, package-size-adjusted unit prices, fees, and the cheapest combination of store and pickup or delivery method.

Frequent price changes and increasingly layered fulfillment fees have made static price comparisons unreliable. Digital receipts and online carts now provide enough structured evidence to launch a narrowly focused comparison service without direct retailer cooperation.