> A $120M spend on AWS is equivalent to around a $12M spend on Hetzner Dedicated (likely even less, the factor is 10-20x in my experience), so that would be 3% of their revenue from a single customer.

I'm not convinced.

I assume someone at Netflix has thought about this, because if that were true and as simple as you say, Netflix would simply just buy Hetzner.

I think there lots of reasons you could have this experience, and it still wouldn't be Netflix's experience.

For one, big applications tend to get discounts. A decade ago when I (the company I was working for) was paying Amazon a mere $0,2M a month and getting much better prices from my account manager than were posted on the website.

There are other reasons (mostly from my own experiences pricing/costing big applications, but also due to some exotic/unusual Amazon features I'm sure Netflix depends on) but this is probably big enough: Volume gets discounts, and at Netflix-size I would expect spectacular discounts.

I do not think we can estimate the factor better than 1.5-2x without a really good example/case-study of a company someplace in-between: How big are the companies you're thinking about? If they're not spending at least $5m a month I doubt the figures would be indicative of the kind of savings Netflix could expect.