Exactly, 1000 PRs per week probably equates to around ~100 engineers worth of output.

Hard to do an exact ROI, but they're probably saving something like $20,000,000+ / year from not having to hire engineers to do this work.

They are enforcing rigor, on agents, the same way they would on humans. Do people think Stripe's engineering team would have been able to progress if each individual (human | machine) employee was not under harness and guardrail, and just wrote code willy nilly according to their whims? Vibe coding is whimsical, agentic engineering is re-applying what brought and brings rigor to software engineering in general, just to LLM outputs. Of course, it's not only that and there are novel problem spaces.