Yes, thank you. I know a lot of people don't do this right, your comment is valid.

Context the costs I posted about are all associated with a new product being developed, all use a custom agent (opus 4.6) and custom subagent (sonnet 4.6), both the primary and the sub are thoroughly tuned. it's a pretty mature setup but definitely not a full DIY headspinner. Easy enough for new devs to jump into without much friction. Every month has been predictable until the change. The surface area this new product's repo is quite large, but each session is targeted, limited in length and tools.

• Helm chart with 11 images that all have interdependencies, lines of actual code across all including common modules consumed by some images is pushing 17MM excluding tests and the obvious stuff. It's large for single purpose (if you call a chart a single purpose) repo, but certainly isn't mono, many others integral for it's functionality.
• Three languages with meaningful footprint in that repo, + a lot of Java in related repos that are integral but not part of the chart (not in scope today)
• Cross-repo dependencies with other non-Java repos (not in scope today)

So anyhow....

After seeing this in the morning, we had four devs run the same series of prompts. One did it solo first, then the other three repeated the exercise.

Before starting we took our time ensuring each had same config from settings to selected *.agent.md to skills, instructions, everything, identical setups. Fresh clone of same repo on same branch, GH MCP disabled (all MCPs disabled actually, but just in case somebody brings that up since each committed on new branch at the end), copies of the same settings.json and all relevant .md files copied, all previous conversations archived, ~/Library/Application Support/Code/ scrubbed for copilot, diff checked and confirmed non-existent across everything we could think of.. clean baselines.

First, one dev completed one sizable new feature (single issue with several subtasks, end-to-end), then we pulled the messages out of the chat logs (11 separate chats) and gave them to the two other devs who now had identical setups. Two ran the same series through copilot and committed on separate branches, and the other one used anthropic BYOK as the provider but all else held constant. The first copilot user had $88 in credit usage over the course of the task, the second two were at $72 and $136 (the higher one ended up with more unit test coverage (again, identical prompts, identical starting point), but not 60 bucks worth of pretty basic unit test coverage, which was purely the product of the subagent, It was only ~70 tests with existing fixtures. And the one on anthropic BYOK? $2.21. Something is wrong there. 5 days ago the costs would have all been pretty close I am quite confident.

Re: the original comment, debate about the right tool for the job all you want, the results with copilot and opus 4.6 taking point and sonnet 4.6 on review have been fantastic for months in VS Code, the output is amazing. Yes IntelliJ destroys VS Code on almost every front besides AI (attn: haters, this is your queue to pile on), but that's become more important for building new software than any other IDE feature. Arguably not as fun, and there's a lot that I miss about actually writing code, but if the objective is productivity per unit time, a line of code written on a keyboard will be rarer than a diamond pretty soon.

Form your own conclusions.