There is overhead for space, reliability, networking, and maintenance for bare metal. If you have an existing datacenter the marginal costs are tiny, but if you are only in the cloud or not planning to need these beasts for years on end, the net costs are much lower to just harness the economies of scale provided by GCP, AWS, et al. As for OVH, the amount you’d save in networking between that box and the rest of your infrastructure by having everything on one cloud provider probably pays for the difference.

Add in flexible network storage options and integration with existing security infrastructure. You are thinking too small by comparing a single box to a single box.