If you only need a server, as in CPU, RAM, disk and bandwidth, with a more or less constant demand, then sure, a dedicated server is way cheaper than any cloud.

If you only need a server, as in CPU, RAM, disk and bandwidth, with a more or less constant demand, then sure, a dedicated server is way cheaper than any cloud. You want to use cloud for the ecosystem of other services besides VM/instances, and especially to use them in an automated way. The other use case is elastic demand.