It's more than a server, it's the whole rack with networking and all that, integrated and with unified management.

There is some company who for reason X and Y rather (or are obligated to) do on-prem for their hosting needs. But setting up a full (or several) racks, with all the required equipment for proper networking, storage, etc, can be quite the hassle. And if you want cloud-like functionality (completely API manageable virtual network, VM, storage pools, ...) it's another can of worm. Having a "plug'n'play" cloud-like system on-prem that do not require several engineers who know 10's of different vendors tech is definitely worth the premium for those company.