A store (I think) I can recommend for cheap Windows Keys

[FlyingPenguin]

https://digitalchillmart.com

Found these guys mentioned on some Reddit forums as reputable. They only sell retail keys, not unused OEM keys like a lot of these key vendors. I did some searches on their name and only hear good things. Keys almost always work, and the few people that have had a problem quickly got another key by contacting support.

I'm building a new file server and needed a Win10 Pro key. I have a physical one I purchased at full retail a few years ago, sitting on my shelf as a spare, but I thought this might be an opportunity to try out the gray key market.

Purchase was simple. They have a proper store. They don't take Paypal (they used to) so I just used a one-time Privacy.com virtual card so I didn't have to give them one of my real card number (they seem to have some other options like Google Pay).

The key cost $25, and you get it instantly - not like other sites which I hear send it to you via email after a delay.

I checked it's validity using the ShowKeyPlus utility, and it did come up as a retail key, not an OEM key.

It activated without any issue.

So, a tentative recommendation. The fact that it's a retail key means it's not a violation of Microsoft's license to sell it, but as with anything gray area, buyer beware.

NOTE: I would recommend installing the key immediately, because they do email you an invoice that contains the key. If you let that key sit around a while, someone else might use it. Once you've activated it, it's locked to your hardware.

[FlyingPenguin]

BTW: Another store that was highly recommended is https://vendafly.com/

I have no personal experience with them, though. They are reputed to also sell only retail keys.

[Losbot]

Good to know, as I am about to deploy a new Windows VM at home.