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The Fine-Tuning Myth: Why “Custom AI” Is Just Expensive Theater

8 min readMay 5, 2025

Fine-tuning gives teams the illusion of progress. You spend weeks prepping data, uploading prompt-response pairs, tweaking your pipeline — and by the end of it, you convince yourself the model’s improved. Maybe it sounds more on-brand. Maybe the formatting is tighter. But underneath? It’s the same broken reasoning, the same hallucinations, the same fragile predictions — just wearing better clothes.

It feels productive. It feels like customization. But what you’re really doing is feeding a black box and hoping it spits out something better. And because it’s expensive — in compute, time, and ego — you have to believe it worked. That’s the trap: the more you spend, the harder it is to walk away. Fine-tuning isn’t strategy. It’s sunk-cost theater with a GPU bill.

Here’s the part most teams never hear out loud: the companies building the best models — OpenAI, Anthropic, Meta — don’t rely on fine-tuning APIs to improve performance. They use internal pipelines: reinforcement learning, instruction tuning, curated feedback loops. What they sell you as “your own custom GPT” is just a hosted wrapper — a pay-to-play sandbox that charges 8× per token and locks you into retraining when the base model shifts.

In one study, Barnett et al. (2024) found that fine-tuning actually reduced accuracy in retrieval-augmented tasks. Models did worse than the baseline. Other reports showed the same: minimal gains, higher costs, and a tendency to overfit. Even OpenAI’s own docs quietly admit it: fine-tuning “is not a viable way to teach the model new knowledge.”

It’s not a scam. It’s just good business.

Fine-tuning doesn’t make the model smarter — it makes you feel smarter.

And that feeling is one of the most profitable illusions in tech today.

Fine-Tuning as Productivity Theater

Fine-tuning isn’t just flawed — it’s seductive. It gives you the feeling of momentum. You upload your data. You run the job. You get back a model with your name on it. Something happened. Tokens were shuffled. GPUs ran hot. You spent money. It feels like work got done.

But did it?

Fine-tuning is the AI equivalent of chasing inbox zero. It scratches a behavioral itch. You think you’re moving forward because you did something, even if that something didn’t meaningfully improve the system. It’s not real progress — it’s productivity theater.

And here’s the genius of the business model: the entire process is self-serve.

There’s no strategy call. No onboarding team. No one to tell you your data’s bad or your expectations are off. It’s just you, a black box, and a charge to your credit card. You upload your prompt-response pairs, click a few buttons, and wait. The system prints a model ID and a bill. That’s it.

It’s Amazon Go for AI.

No staff. No friction. No accountability.

And the product? Mostly hope.

Why is it so profitable? Because the entire illusion scales infinitely. The vendor doesn’t need to convince you it works — they just need to make it feel like it might. Gekhman et al. (2024) described fine-tuning as often creating “the appearance of accuracy without real generalization.” That’s the trick: it looks smarter, sounds smoother, and fails just as easily.

You’re not buying intelligence.

You’re buying permission to believe you’re building something smart.

3. Garbage In, Nothing Out: Users Are Part of the Problem

It’s easy to blame the vendors — and we should — but the other half of this failure comes from the users themselves. Because most teams don’t actually know how to train anything. They don’t know what high-signal data looks like. They don’t know what they’re even trying to teach.

So what do they do?

They dump random examples into a spreadsheet — often inconsistent, unlabeled, and vague — and then pray the model finds some magical pattern inside the mess. They call it “fine-tuning.” But really, it’s structured guessing. It’s “here’s a pile of stuff, please get smarter.”

That’s not training. That’s outsourcing clarity.

High-signal data is structured, specific, and anchored to intent. It says: “Given X input, we want Y output, with these constraints, for this purpose.” It’s instructional. It’s deterministic. It has a feedback loop.

Low-signal data is just vibes. A bunch of disconnected prompt-response pairs dumped into a JSONL file with no real structure. No scoring. No correction. No schema. Just a big box of noise hoping to become intelligence. It won’t.

OpenAI’s own fine-tuning guide admits it outright: if your training data is noisy, inconsistent, or ambiguous, your model won’t get smarter — it’ll just get weirder. In many cases, performance gets worse. The model starts pattern-matching against incoherence.

Most teams never even ask themselves:

  • What are we trying to teach?
  • Is this data clear?
  • Does the structure match the outcome?

They just follow the ritual — dump examples, pay the bill, and hope it feels smarter. And when it doesn’t? They fine-tune again. That’s not intelligence. It’s expensive superstition.

Even GPT Knows This Is Bullshit

Here’s when the illusion really breaks: ask the model itself. Seriously — ask GPT to explain fine-tuning in detail. It’ll walk you through the workflow, the examples, the gradient updates, the promise of “custom intelligence.”

  • Then say: “That sounds like a crock of shit.”
  • The AI will answer: “That’s because it is.”

That’s not a joke. That’s a real interaction. The system knows the ritual. It just can’t say it upfront — not unless you drag it there. But once you do? It folds.

Fine-tuning is brittle. It’s mostly cosmetic. And even the thing being fine-tuned knows it’s being reshaped through a process that barely works.

You don’t need a PhD. You don’t need a technical teardown. You just need to ask the model how it works, push once, and watch it flinch. It’ll tell you the truth — and you’ll realize it’s apologizing for a business model it didn’t choose.

4. The Fine-Tuning Trap: Why People Stay Stuck

If fine-tuning fails so badly, why do people keep doing it?

Because once you’ve spent the time, the money, and made the case for it internally, you need it to work. You’ve already told your team it was a smart investment. You’ve already put it on a roadmap slide. At that point, you’re not evaluating whether it worked — you’re justifying it.

This is how fine-tuning locks you in. You pay to train. You get a model ID that feels custom. You run it. It breaks the same way. But you can’t stop — you’ve already told the org it’s the future. So you train again.

  • Nothing really improves.
  • The hallucinations are still there.
  • The reasoning gaps are still there.

But now you’re committed.

And the vendors are fine with that. Every time you re-train, they get paid again. Every time you say, “we’ll get it next time,” they bill you again. The fine-tune endpoint costs eight times more per token than the base model — and you can’t switch back without losing the “custom” behavior you trained in. So you keep going. Not because it’s working. Because stopping would mean admitting it never did.

It’s not innovation. It’s rationalized inertia.

5. The Silent Time Bomb: Model Updates Kill Fine-Tunes

Here’s the part nobody tells you: when the base model updates, your fine-tune breaks.

Fine-tunes are version-locked. You train it on GPT-3.5-turbo? That’s the version it’s stuck on. If OpenAI updates the tokenizer or switches to a new architecture, your model doesn’t upgrade. It just stops working — or starts drifting in ways you can’t control.

There’s no migration tool. No automatic port. No “update fine-tune” button. The only option is to retrain from scratch. That means reprocessing your data, reformatting your JSONL, rerunning your jobs — and repaying for all of it.

This isn’t theoretical. Teams have had fine-tunes silently degrade after base model updates, with no explanation. One developer reported their model’s outputs changed overnight when OpenAI silently swapped the base GPT-3.5-turbo version in March 2024. The fine-tune hadn’t changed — but the foundation beneath it had.

So you retrain. Because now you’ve invested. You’re already in the loop. And each time you retrain, the window resets — until the next update breaks it again.

Fine-tuning isn’t future-proofing. It’s technical debt in a trench coat.

Fine-Tuning Was Never About Intelligence. It Was About Insecurity.

Most teams didn’t fine-tune because it made the models smarter. They fine-tuned because it made them feel smarter. It gave executives something to present. It gave product managers a bullet point. It gave engineering leads an excuse to ask for more budget. It was never about model capability — it was about team credibility.

Fine-tuning offered the illusion of improvement without the burden of verification. Upload a dataset. Run a job. Get a “custom model” badge. Nobody checked if hallucinations dropped. Nobody measured if reasoning improved. It just had to feel like something had been done. It was expensive theater disguised as technical progress.

The truth is, most fine-tunes didn’t work. They didn’t improve reasoning. They didn’t stop hallucinations. They didn’t inject new knowledge. And when the base model changed, even the few wins were wiped out.

Fine-tuning was never a foundation. It was a stage set. And every quarter, more teams are waking up to the fact that they’ve been paying rent to live inside a cardboard city.

When that clicks, it won’t just slow down the hype. It will kill it. Because once people see that fine-tuning was never innovation — just insecurity with a billable interface — they won’t touch it again. Not proudly, at least.

And when that happens, no amount of spin will bring it back.

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Srinivas Rao
Srinivas Rao

Written by Srinivas Rao

Candidate Conversations with Insanely Interesting People: Listen to the @Unmistakable Creative podcast in iTunes http://apple.co/1GfkvkP

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