[wongarsu]

Upgrade keys for Windows 10 pro are cheap on eBay and are completely worth it.

[kristianp]

Aren't they unauthorized volume keys that are likely to fail activation?

[wongarsu]

Yes, they are volume keys. Check the legal situation in your jurisdiction before buying.

I've had one out of about ten fail on activation. But they cost 1/40th of what Microsoft is charging, so I don't mind that.