We've been running these numbers ourselves lately as well. We find AWS much more expensive. For instance, we bought a Dell 2950 / 2xQuad Core / 12 GB RAMB / 4

We've been running these numbers ourselves lately as well. We find AWS much more expensive. For instance, we bought a Dell 2950 / 2xQuad Core / 12 GB RAMB / 4x500GB RAID 5 w/hot spare for ~$4500. We have it in a colo where it costs about $150 a month for the space + bandwidth. This is about equivalent to the $750/mo extra-large instance. There will also be additional AWS fees for transfer, storage, etc, but we'll go with $750 for simplicity. That's a $600/mo premium, or $7200 a year. So I pay for the hardware within 8 months and after that it's $600 a month savings. There is a lot of value in being able to provision extra server quickly, use cloudfront, etc, but it comes with a high price, IMO.