Their revenue is like $670bln. If you come up with an innovation that increases that by 0.01%, say by better optimizing prices or targeting adds, you've added $60m of revenue. If you pay a star engineer $1m per year and they have even a reasonable chance of an improvement on this scale, or a similar reduction in costs, then you have a super profitable deal.

I don’t think anyone in senior management actually thinks like that. The company works on a plan (for better or worse), and the resources needed to fulfill it.

There are teams for maintaining massive services where you can build promo packets with a couple <1% cost reduction PRs. I've worked on a non Amazon but similar team where half our M2's org charter was explicitly cost reduction with KPIs of x dollars saved (measured using CPU/memory/etc that we had formulas to convert to infra dollar equivalents).

It's a pretty non trivial problem to build and maintain infrastructure and customer relationships at that scale, yes, including the myriad of services they provide other than just "compute slices".