Well, I would say two things in response to this... that if anything the costs totaled up here are pretty inflated (read: vastly so).
First, you generally aren't going to be paying (or paying much) for reasonable connection speeds at colocation facilities. As someone noted already, many times it's included with a large enough contract. I know in my case we're essentially paying $2.5k/month for a full cabinet and a connection... essentially dirt-cheap and not in a rinky-dink colo facility either.
As for the hardware, you have to figure that to spin up 50 application servers on 50 sessions at Amazon is nowhere near the same as 50 sessions on your own hardware. If you virtualize, like the EC2 backend is of course, you're not sharing the hardware with anyone. You don't need to worry about noisy-neighbors or I/O issues if you've purchased the right hardware. Essentially I'd go out on a limb and say you could at least halve those hardware numbers.
In my experience from physical to virtualized systems, even under high-load situations 90% of your 'load' issues are not going to come from processors, but from memory limitations, so yeah... hardware costs I expect will be lower than calculated... much lower.
From a "what you get" perspective I totally agree with you. I simplified the comparison to core count to have an easier basis to setup the rest of the analysis.
I would not be the least bit surprised if I halved those hardware numbers and it kept up just fine; mostly for the reasons you pointed out.
First, you generally aren't going to be paying (or paying much) for reasonable connection speeds at colocation facilities. As someone noted already, many times it's included with a large enough contract. I know in my case we're essentially paying $2.5k/month for a full cabinet and a connection... essentially dirt-cheap and not in a rinky-dink colo facility either.
As for the hardware, you have to figure that to spin up 50 application servers on 50 sessions at Amazon is nowhere near the same as 50 sessions on your own hardware. If you virtualize, like the EC2 backend is of course, you're not sharing the hardware with anyone. You don't need to worry about noisy-neighbors or I/O issues if you've purchased the right hardware. Essentially I'd go out on a limb and say you could at least halve those hardware numbers.
In my experience from physical to virtualized systems, even under high-load situations 90% of your 'load' issues are not going to come from processors, but from memory limitations, so yeah... hardware costs I expect will be lower than calculated... much lower.