I believe AWS struck the right balance to "Think Big" and not worry about minutiae at the beginning, while tightening the belt and ensuring costs are not out of control at later stages. One of my teams was given the charter to map the entire world's Internet weather map. This service collected billions of data points every 5 mins and we spent many 10s of millions doing it. But as soon as the innovation phase was over, I had to take a goal and start an MBR (Monthly Business Review) to drive the costs down. This was a really interesting mechanism which doesn't stifle innovation in the short-term but doesn't let costs go crazy in the long-term.
Did you see a similar pattern in EC2?
In particular, there was a strong understanding that engineers would overfocus on optimizing for what was asked, and so the deliberate overfocus was on "thinking big" on products that could grow rapidly while having pricing and engineering models that may be neutral margin in the short term; only in the long term paying off as positive margin (without needing to "surprise" customers with a price change).