And all you need to do is pay a sysadmin or two in pizza to operate them :-)
Dedicated servers are undoubtedly cheaper in some circumstances than even a well-managed AWS account. But you do need to account for redundancy (including staffing), scaling up, possibly geographic replication, etc.). Setting up a dedicated server is just the beginning and be sure to take into account all costs--as is the case on a cloud provider too of course.
You absolutely need experts to run your cloud aswell, and there are colocating services that offer staff on hand for hardware issues, you don't actually have to run an entire datacenter even if you run baremetal