I wanted to add more info but couldn't edit. We bought that server for $12,000 with 5 year warranty, and got our Windows Server licenses out of an MS bundle which cost about $400.

I think that brings the ROI after 5 years compared with AWS to something like 3200%, less energy, if nothing goes wrong.

(I know that there are better options than running Windows Server on this box, but it seems to perform the same, it's far easier to administer by inexperienced devops, and in the long term it's actually around $1500/yr cheaper than running supported RHEL. Our other box is running supported RHEL but after testing Windows Server and having no issues we'll probably switch it for the cost savings).