Lesson 13 of 14 · Smart & safe · 3 minutes
Saving money: cheaper ovens, shorter prompts, caching
Most bakes cost a fraction of a cent, but a recipe that runs every hour adds up. Here are Granny's three biggest savings, from biggest to smallest.
1. A cheaper oven
The oven is by far the biggest lever. Prices between ovens differ a hundred times or more. Here is the same real email from a dear oven and a cheap one:
The message Write a short, kind email to a customer whose cake order will be one day late.
Real answers from GrannyBakes' model demos. Compare the cost under each answer.
Chat Latest
A big oven with a big priceInstructions sent
You help a small family bakery write to its customers.
Subject: A Small Delay with Your Cake Order
Dear [Customer’s Name],
We’re very sorry to let you know that your cake order will be ready one day later than originally planned.
We understand how important your order is, and we sincerely apologize for any inconvenience this may cause.
We’re taking extra care to make sure your cake is just right, and we truly appreciate your patience and understanding.
Thank you for supporting our little bakery! ❤️
Warm regards,
[Your Bakery Name]1.6 s · 39 in / 104 out tokens · $0.0033
GPT-6 Luna
A small oven with a tiny priceInstructions sent
You help a small family bakery write to its customers.
Subject: Update on Your Cake Order
Hi [Customer Name],
I’m so sorry, but your cake will be ready one day later than planned, on [new date]. We apologize for the delay and appreciate your understanding. Please let us know if this causes any inconvenience.
Warmly,
[ Bakery Name ]2.8 s · 39 in / 95 out tokens · 25 of them thinking · $0.000051
Both emails are kind and clear. For everyday jobs, a small oven is often just as good. When Granny sees a step that a cheaper oven could do, she shows a 💡 suggestion with the saving. She never switches by herself: try it side by side first, and Undo is always there.
2. Shorter prompts
You pay for every input token, on every message. Long instructions, long chats and many Pantry pieces all add up:
- Keep instructions short and clear.
- Use the "forgets after each message" memory for one-shot jobs.
- Start a new chat for a new topic.
- Hand over 3 Pantry pieces instead of 10 if that's enough.
3. Caching
When you send the same long start of a prompt again within a few minutes (the same instructions, the same chat), OpenAI recognizes it and charges much less to read it: often a tenth of the price. This caching happens by itself. It's one more reason to keep instructions the same and put what changes at the end.
Check before you switch
A taste test runs a few sample inputs on a baker or recipe and shows the answers, the time and the cost side by side. Run one before and after a change, and you'll know whether the cheaper oven still bakes well.
Granny's rule of thumb: change one thing at a time, and taste-test it.