Earlier quoted context omitted.
Yup, they are very serious about DynamoDB and it is a very good product. Wish they released more information about it, though.
They have published 2 academic papers about it. What more do you want, operational details?
One blog says it is charged by the amount of change logs (but the official doc doesn't say so), which makes sense. But how do I estimate the amount? My hunch is: Put + Write + (1~100) * TransitWrite + Update + Delete + (1~25) * BatchWrite.