A version of the 2019 Mac Pro that can be mounted on server racks is now available for purchase starting at US$6,499.
Rack-Mounted Mac Pro
This version is the same Mac Pro with the same configuration options. But instead of using wheels like standard Mac Pro it uses stainless steel slide rails to be mounted onto a server rack.
The base model for the rack mounted Mac Pro is the same as the standard model: 32 GB of RAM, 3.5GHz 8-core Intel Xeon W processor, and 256 GB of storage. The price is really the only difference, because the standard model starts at US$5,999.