Well, I was ultimately commenting on margins. Since we agree that at scale, DIY is cheaper, that implies to me that AWS margins are healthy.
On point 2&3, there are plenty of cloud offerings, the more you use premium features, the more you are locking yourself into to one provider.
I would say that the greatest additional benefit over traditional hosting is low startup cost and autoscaling. But once you're established, if you're using those premium features, you're stuck, so your business better have high margins too.
