Costco vs Amazon

Which store actually wins?

Side-by-side unit-price math for Costco and Amazon — because pack sizes never match, and sticker prices lie.

Sample data only. This demo ships with illustrative, fictional prices — not live data. Add your own items below, or import a CSV. Always verify current prices with the retailer before buying.

Compare prices

ILLUSTRATIVE SAMPLE DATA — these prices are fictional examples, not scraped and not current. Read the methodology and verify before purchase.

Add your own item

Items you add are stored only in this browser (localStorage). Nothing is uploaded or shared. You can export them as CSV for backup.

Backup & import

Export everything (sample + your items) as CSV, or import a CSV of your own items.

CSV columns: name,brand,category,size_label,costco_price,amazon_price,unit,costco_units,amazon_units,blurb
Only import prices you have the right to use — do not import data scraped from retailer sites in violation of their terms. See the Terms.

Data sources Advanced

Optionally connect your own JSON price endpoint and merge its items into the comparison table. This is a generic connector — we do not provide integrations for scraping Amazon, Costco, or any specific retailer, and nothing here helps circumvent any site's terms or protections.

Only connect APIs and data sources you have lawful access to and whose terms permit this use. You are responsible for complying with your API provider's terms — this app is only a viewer for data you lawfully obtain. Only use API keys you own or are authorized to use. Your key is stored only in this browser and is sent only to the endpoint URL you configure.

Must return JSON: an array of products, or an object with a products, items, or data array.

No key saved.

Field mapping (which JSON fields hold what)
Browser limitation: your endpoint must allow cross-origin browser requests (CORS). Many APIs block direct browser calls — in that case use a CORS-enabled endpoint or your own proxy. We don't provide a proxy service and never will.

Price history

Snapshots of your data source, stored only in this browser.

Methodology

How the comparison works

Costco and Amazon rarely sell the same product in the same pack size, so comparing sticker prices is misleading. For each product we compute the unit price at each store: the listed price divided by the quantity of a common unit (oz, fl oz, lb, count, roll, ft, or each). The store with the lower unit price “wins.”

The $ savings figure shows what you’d save by buying the Costco-sized pack at Costco’s unit price versus paying Amazon’s unit price for that same quantity. The % savings is the unit-price difference relative to the more expensive store’s unit price.

About the data — read this before trusting any number

  • The built-in dataset is illustrative sample data only. Prices are fictional examples, written to look plausible. They were not scraped from any retailer, are not live, and are not current.
  • Verify before purchase. Always check the actual price at the retailer before buying. Prices change constantly and vary by location, membership, and promotions.
  • Taxes, shipping, and membership costs are not included in the math.
  • Items you add are stored only on your device and never leave it.

No scraping, ever

This project never scrapes retailer websites and never calls retailer APIs. The dataset is hand-written sample data plus whatever you type in yourself. We do not provide or encourage automated price collection, and nothing here should be used to violate any website’s terms of service.