Around $2k per year isn't unreasonable per server in a large data centre. This also roughly correlates with what a colocated server would cost.
The way fishtrain has based these figures is all around capital expenditure - most companies wouldn't actually do this.
Facebook is running order of magnitude 10k servers. So in that respect his "servers required for the load" figures are about right.
Taking $2k, then fishtrain's annual estimates for ~10k plus servers is too low - it would be more like $20m. Again, the way fishtrain has gone about it wrt to CAPEX is different.
The electricity consumption seems a bit high, but for a business plan it might not be unreasonable.
Bandwidth - well that depends totally on your application.
Commissioning a server isn't necessarily cheap - there is the cost of the server itself, the labour, networking, test, etc, etc. This can be a fairly significant one-time cost (and isn't capitalised).
People tend to worry about the ongoing cost of storage a bit too much, particularly if you're retaining a lot of data (e.g. keeping people's images). The fact is that the cost of storage steadily decreases, so this usually amortizes this in reality. So I'd say you'd only need to worry about the increments in most cases - unless your application is horrendously storage hungry.
