However I am not sure how much is strictly necessary.
I honestly think a small team could achieve lot more . You loose the agility of smaller team at >50 have large company problems without the benefit of sheer manpower 500-1000 typically brings.
Scaling devops is not as hard as it sounds . There are plenty of cloud native services which scale pretty well more or less out of the box( you still domain knowledge I.e. need to know that service’s unique limitations)
scaling it for cheap is harder, still not as hard as it used to be, plenty of mature tech is available today. Ironically devops engineers with modern cloud skills generally are more expensive than the ones who know how to stand a server in a DC.
A lot of startups like WhatsApp , Instagram built great products at scale with less than < 50 so it not impossible to achieve