If you want to do literally the exact same task in literally the exact same configuration and ideally the exact same input data, then yes, it costs the same. But that solution is as permanent as it is useless.

A tool for generating a report for September 2026 is no more expensive than an agent generating a report for September 2026. But that tool is useless for you in October 2026. You'll need to generate a whole new tool for October 2026, and generating 2 tools costs as much as generating 2 reports so you're not saving anything.

Making a tool that can generate a report for any single month can easily cost 10 times more than a single report, entirely due to the extra code flow analysis required to extract the right variables in the right places. And that's without any UI. If you want UI that's another several times more tokens because UI is hard. Also it will suck compared to a simple chat window where you can ask the assistant for anything and it will understand. If you want UI that's better than the chat, that alone costs you more than everything you spent so far.

All in all, your permanent solution starts paying for itself in about 4 to 6 years, assuming you never had to update how the report is generated in the meantime.

Or you could have a very simple, very cheap script that only gets run once then gets deleted (or even better, kept for future reference to make future report scripts even cheaper to generate).

Note that this is all in the hypothetical future where AI is actually capable of one shotting such a task. If it makes mistakes, then human-made apps are still the most cost-effective option and this whole discussion is moot.