I built my own server for home last year, all consumer hardware (AMD Ryzen, 96GiB RAM, NVME SSD, HDDs etc). Total cost was ~£3,000 at the time - £6000 up front cost for a business seems reasonable; and you could get away with less.
However, the main cost would be colocation - it's risen quite a bit.
However, the main cost would be colocation - it's risen quite a bit.