This is very theoretical and won't hold up in the real world. You also need to factor in the costs of hot standby equipment (can you provision a server with 68G

This is very theoretical and won't hold up in the real world. You also need to factor in the costs of hot standby equipment (can you provision a server with 68GB RAM within minutes?), service (whom do you pay and how much for a) servicing your hardware b) being on standby to fix issues within single hours). You need to train your people that will maintain the physical servers. You need to factor in the probability of their mistakes (in my experience from a supercomputing center most problems were caused by people touching equipment). And of course when you get mentioned on CNN you need to be able to handle the traffic peak. Runnning a real world operation really isn't as simple as adding numbers from a colocation price table.