Build a household price book that actually changes what you buy

Start with repeated spending

Do not catalogue the entire supermarket. Begin with products your household buys at least every two months and categories where prices vary meaningfully. Toilet paper, detergent, coffee, pet food, diapers, and trash bags are better candidates than nutmeg.

Normalize before recording

Choose one unit for each category: 100 sheets, square feet, loads, ounces, bags, or count. Record the final price after generally available discounts, along with the retailer and date.

Set three thresholds

The usual price tells you what waiting costs. The good-buy price justifies purchasing the next needed package. The excellent-buy price justifies buying enough to bridge multiple sales cycles.

• ✓Usual: common shelf or online price
• ✓Good: meaningfully below normal
• ✓Excellent: near the lowest repeatable price

Let the system stay small

Review thresholds every few months, not every afternoon. The purpose is to make recurring purchases easier and cheaper—not to spend one’s finite life force monitoring dishwasher tablets.