* An air-conditioned room + maintenance (this could be very large if you are a big company) * How many staff at $50-100K per year to look after it * How to deal with internet reliability - do we need multiple high bandwidth broadband links at $1000+/month? * Ongoing op-ex costs for failed components. * Cap-ex replacement of hardware after 2-3 years
The point of the cloud is that these costs are wrapped up in your rental cost so of course it looks high.
If you have the people/skills and need control over exactly how your hardware is provisioned, go on-prem and good luck but plenty of us would rather concentrate on what we are good at and are happy to pay 50-100K per year to a cloud provider to do it for us.