BYOK vs credit packs: the hidden cost of AI in spreadsheets

"$29 for 50,000 AI calls" looks like a deal. The number is round, the math feels intuitive, and you stop thinking about it. That's the point.

This post is the math you should have done before you bought the pack.

Two business models

Every AI spreadsheet add-on sits on one of two foundations:

1. Credit packs (resold tokens). The vendor pays OpenAI / Anthropic for tokens, marks them up, and sells you "credits". You buy a pack; calls debit from it. When you run out, you buy another.
2. BYOK (bring-your-own-key). You pay the LLM provider directly at list price. The vendor charges you a fixed software fee — one-time, lifetime, or monthly — for the add-on itself. Your calls go straight from your browser to OpenAI / Anthropic / Google. The vendor doesn't see a token.

The user experience is similar. The economics are very different.

What you're actually paying

Take a typical AI-in-Sheets call: 200 input tokens, 30 output tokens, model gpt-4o-mini. The actual cost to OpenAI at list price is $0.000048 — that's 48 millionths of a dollar.

Now look at the math behind "$29 for 50,000 credits". Most packs spend ~1 credit per call. That's $0.00058 per call — about 12× the OpenAI list price. The vendor's margin is the difference.

This isn't malice. They have a real business to run — engineering, support, compliance, billing, infra. The markup is how they fund it. But the markup is also paid by you, on every call, forever.

The crossover point

Here's what the same workload costs at three usage levels, assuming a $49 lifetime BYOK license vs a $29/month credit pack (50k credits, then $0.001 per overage credit):

Below 5,000 calls/month, credit packs are perfectly fine — and the cognitive overhead of getting an API key isn't worth saving $20. Between 50,000 and 200,000 calls — where most serious users land — BYOK starts to pay for itself within the first month. Above 200,000 calls, the gap is hundreds of dollars a month.

The other costs you don't see

Data flow

With credit packs, every cell call routes through a third-party server. That's where billing, rate-limiting, and abuse detection happen. It's also where your prompts and cell contents land in plaintext, even if briefly. If your sheet has PII, customer messages, internal pricing, or anything under NDA, that's a compliance review your privacy team will not enjoy.

With BYOK, calls go from your browser to OpenAI / Anthropic / Google directly. The add-on author never sees the request. Your data path is one hop shorter, and the only third party you trust is the LLM provider you'd be using anyway.

Vendor lock-in

Credit packs are usually tied to one provider. If GPT-5 launches and Claude is now better at your specific task, you can't just swap — your credits are denominated in their resold-OpenAI flavor. Want to use Claude? Buy a different pack from a different vendor.

With BYOK, you paste a Claude key alongside your OpenAI key. The formula picks the provider per call. Use the cheapest model for the task, every time.

Sunk-cost waste

A credit-pack month is "use it or lose it". Buy 50,000 credits in January, use 12,000, and you paid for 38,000 you'll never see. BYOK has no calendar — your $49 lifetime license keeps working in May 2027 with no further payment.

When credit packs make sense

Two cases:

• You're below ~500 calls/month forever. Light user, occasional cell here and there. The $20-ish difference isn't worth the 5-minute key setup.
• You can't get an API key. Some orgs lock down developer accounts. If your IT won't issue you an OpenAI key but will approve a sanctioned spreadsheet add-on, take the credit pack.

For everyone else, BYOK is structurally cheaper. The reason credit-pack vendors don't lead with the cost comparison is that they can't — the math doesn't work in their favor above a few thousand calls.

"But I'm not running 200,000 calls"

True. Most people aren't, on day one. Here's how usage actually grows:

1. You install the add-on for one specific task — a one-off CSV cleanup, say.
2. It works. You start using it weekly. ~500 calls/month.
3. You add a second use case — auto-tagging incoming leads. ~5,000 calls/month.
4. Someone on your team sees it work, asks for help, you build them a similar sheet. ~15,000 calls/month.
5. You discover Bulk Apply / scheduled imports. Run a 10,000-row monthly classification. ~30,000 calls/month.
6. You start using the chat agent + connectors for ad-hoc analyses. ~75,000 calls/month.

By step 5 you've crossed the BYOK breakeven. By step 6 you're saving $100/month vs a credit pack. The decision you make at step 1 sets the cost trajectory for the whole curve.

BYOK is the kind of decision that looks identical on day 1 and looks very different on month 6. Future-you will not be sorry.

How gptsheet's pricing works

gptsheet is BYOK. You pay once — Starter $49, Premium $99, Pro $199, Max $299 — and you're done. The license includes lifetime updates. Your OpenAI / Anthropic / Gemini bill goes to OpenAI / Anthropic / Gemini, at their list price, with no markup. Most users spend $2–$10/month on LLM calls; you'll see your bill in those companies' dashboards, not ours.

If you're light enough that credit packs are still the right call — great, save the $49. If you're heavier than that, you'll be glad you read this post.