# Opinion: ChatGPT can estimate second‑hand prices but humans must set item boundaries

Digest AI · Marketing & Small Business · published 2026-09-22T02:00:00Z

Canonical: https://digestai.news/story/opinion-chatgpt-can-estimate-secondhand-prices-but-humans-must-set-ite

## Summary

The author fed 60 completed Yahoo! Auctions listings – 30 iPhone 13 128GB items and 30 PlayStation 5 CFI‑1200A01 items – into a fresh ChatGPT session without personalization or external search. In the first test, asking only for a second‑hand market price, ChatGPT returned roughly 35,000 yen for the iPhone and about 55,000 yen for the PS5, matching the author’s own median estimates. The model automatically filtered out mini, Pro, Pro Max, junk, activation‑locked iPhones and empty boxes, set items or units missing controllers for the console.

When the prompt was refined to “standard used units in normal working condition” and the AI was asked to list excluded items, the iPhone price stayed at 35,000 yen while the PS5 price shifted to about 54,500 yen, a 445 yen (0.8%) difference from the author’s median of 54,890 yen. A detailed third test added a full analysis request; the price remained unchanged, but the AI highlighted borderline cases such as a PS5 labeled “unused after purchase” and noted where human verification is needed. The experiment suggests AI can handle data cleaning and median calculation, yet the judgment of what counts as a comparable used item still requires human oversight.

## Key points

- ChatGPT evaluated 60 Yahoo! Auctions listings (30 iPhone 13 128GB, 30 PS5) and output median prices of about 35,000 yen and 55,000 yen.
- When the prompt specified “standard used units,” the AI’s PS5 price changed to about 54,500 yen, a 445 yen (0.8%) difference from the author’s median.
- The AI automatically excluded different models, junk, empty boxes and set items, but struggled with borderline cases like “unused after purchase” that required human judgment.

## Why it matters

Shows that generative AI can clean and average second‑hand data, but final pricing still depends on human decisions about item condition, guiding sellers and platforms on where AI assistance ends.

## Sources

1. [Is it safe to leave second-hand market pricing to AI? I tried feeding 60 real Yahoo! Auctions data points to ChatGPT](https://note.com/ainomakasedokoro/n/nb16532aaaf42?hl=en) (note.com, 2026-09-22)

## Cite

Digest AI, "Opinion: ChatGPT can estimate second‑hand prices but humans must set item boundaries", 22 September 2026, https://digestai.news/story/opinion-chatgpt-can-estimate-secondhand-prices-but-humans-must-set-ite

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