Earlier quoted context omitted.
A good case study is Dropbox. They didn't build any of their own infrastructure until they became big enough (2 years ago).
The fact here isn't quite right. (I'm an employee at Dropbox) Primarily, until 2 years ago we did lean on S3 for all block storage, but most of the rest of the infrastructure (metadata storage, etc) ran in our own datacenters. Your point I think you're getting at sounds like something I'd agree with though -- you can wait a bit the cost efficiency starts to be what is important/impactful to work on before shifting yo…
I don't know if it's true or not but I heard the story.