> For example, suppose an engineer who is paid $200k per year can spend a week to implement an optimization that reduces costs by 0.1%. If that is 0.1% of something that costs $50 million per year, then that's not a bad use of time.

Is it not? I don't know. I don't run a multi-million dollar business. So this is an honest question. 0.1% of $50 million is a meagre $50000. If someone is running a business that is spending $50 million per year on something, are they really going to care about a small $50k saving per year?