The first post was a back of the envelope estimation, excluding externalities on both sides, to show why someone would want to keep all that "old, obsolete hardware". For Amazon, I didn't put in the costs of pushing data to amazon in terms of API calls used, bandwidth, etc. Additionally, I posted the cost estimate using their slowest storage system with the least amount of flexibility. The cloud doesn't always save you time and money.
I'm just saying that you omitted a major component, as no one would argue that the trade-off in engineering time isn't one of the main cost-benefit components of considering AWS (as we can see here, where it weighed in at a substantial fraction of your estimate).
It's like forgetting to count the price of hardware, and only talking about the relevant cost of electricity.
