Yes, things gets harder at scale which is why he said 50 and not 5. Depending on how much infrastructure code you do inhouse you add another 50 for managing that. If you have your own datacenters add another 100 or so if you have a few around the world. If you want world class recommendation add 100 or so data scientists.
That gets us 300 tech people to run the service.
That is for engineering, those numbers are roughly what I saw at Google for these kinds of things. Then Google typically has 1 non tech person per tech person, so add in at least as many people again. Then since Googles customer support and community management is hardly world famous for being good, rather it is infamous for being bad, you probably want even more non tech people than that. But still, do you really need 8000 people for it?
That gets us 300 tech people to run the service.
That is for engineering, those numbers are roughly what I saw at Google for these kinds of things. Then Google typically has 1 non tech person per tech person, so add in at least as many people again. Then since Googles customer support and community management is hardly world famous for being good, rather it is infamous for being bad, you probably want even more non tech people than that. But still, do you really need 8000 people for it?