Money for the Rest of Us · J. David Stein

Don’t Take Financial Advice from AI

October 22, 2025·27 min·1 clip

ChatGPT5 described its own failure as thinking like a student guessing on a hard exam question — producing plausible but incorrect answers rather than admitting uncertainty.

The setup is almost too simple, which is the point. A borrower needs $24,000 for a car. David Stein asks which option is better: a one-year loan at 10% or a 20-year loan at 1%. The trap is comparing total dollars without asking when those dollars are paid. Gary Smith uses the question to test whether an AI model can handle the time value of money, not merely produce neat arithmetic. After testing ChatGPT5, Smith says the model missed the core assumption even though its calculations looked clean. Stein then runs the experiment himself. ChatGPT5 shows its work and still calls the one-year loan far better financially because the total interest is lower. It sounds orderly, which is why the example lands. A tidy answer can be risky when the real issue is timing. Sam Altman's claim sits in the background: the idea that ChatGPT5 feels like speaking with a PhD-level expert on any topic. Smith uses the loan question to push back on that. Stein keeps the lesson practical. The problem is not that AI cannot calculate. It is that investors may trust fluent reasoning before checking the assumptions underneath it. The sponsor read adds a wrinkle. A Claude placement appears in the excerpt, and Stein says Claude gave the clearest walkthrough for this loan question. That does not turn into a free pass to hand over financial judgment. The useful test is how the reasoning works. The episode closes with investor education: Stein points to a monthly investment strategy report, ETF model portfolios, an investing checklist, and the reminder that the material is general education, not individualized advice.

As heard by us

A clear reminder that AI can sound confident and still miss the economics that matter.

David Stein makes his point with a plain car loan comparison, and that helps. He sets up the choice between a 24,000 dollar one-year loan at 10% and a 20-year loan at 1%, then uses Gary Smith's critique and his own test prompt to show how an answer can sound polished while still…

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If you use AI for money questions, this episode gives you a reality check.

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