Show HN: Daily price tracking for Trader Joe's
A small Haskell/SQLite project that tracks Trader Joe’s prices daily via the chain’s public GraphQL API has prompted interest in using granular grocery data to understand inflation, pricing strategy, and shrinkflation. Commenters debate whether Trader Joe’s maintains uniform pricing nationwide, note regional and product-level differences, and suggest enhancements like per-item price history, unit pricing, and alerts for seasonal items. Others broaden the theme to receipt OCR, open price databases, and the potential value—and legal fragility—of automated, long-term retail price monitoring.
Project & Implementation
- Tool tracks daily Trader Joe’s price changes, with source code on GitHub.
- Built around “small but powerful” tooling: SQLite plus scripts; uses Haskell and Nix.
- Prices come from a publicly accessible Trader Joe’s GraphQL API (
/api/graphql), discovered by inspecting web requests. - Current default store is Chicago South Loop; history only goes back a few days because the project is new, but full historical retention is planned.
Price Consistency Across Stores
- Several commenters assert that Trader Joe’s prices are famously identical nationwide.
- Others report concrete counterexamples: higher prices at some LA stores vs. others, and lower prices in the Midwest vs. California.
- Some suggest non-perishables are mostly uniform, while perishable and regionally sourced items differ.
- A screenshot comparison (LA vs. Chicago) shows at least some documented price differences.
- Overall: price uniformity is disputed; likely uniform for many items, but not all.
Use Cases, Features & Extensions
- Many want per-item price history graphs, unit price tracking, and shrinkflation detection (package size vs. price).
- Requests include search filters, sorting, directional arrows for price changes, store selection, and alerts for seasonal items or stock status.
- Some imagine “buy one of everything” calculations and fun edge cases (e.g., cost to wrap the Earth with cheap garlands).
Receipts, OCR & Personal Price Tracking
- One user with years of grocery receipts asks about extracting data to CSV for personal inflation analysis.
- Suggestions: Paperless-ngx, Nextcloud OCR, document scanners, Veryfi for receipt OCR, and using ChatGPT Vision or Excel image-to-data.
- Challenges include inconsistent store codes on receipts and manual mapping of items.
Economics & Business Context
- Discussion around roses’ price spike near Valentine’s Day: seen as classic supply/demand and changing price elasticity.
- Debate over how well Econ 101 models real markets, with mentions of subsidies, regulation, and imperfectly rational actors.
- Some worry Trader Joe’s might shut the API or send a cease-and-desist, given its reputation for secrecy.
- Others discuss Trader Joe’s pricing strategy vs. competitors and broader questions like labor practices and alternative stores.