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

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.