Many cheap keys sold on eBay or discount software sites are "Volume License Keys" (MAK/KMS). These were sold to large corporations to activate many computers.
While Microsoft officially ended support for Windows 7 in 2020, some users still maintain these systems for legacy software compatibility or hardware constraints. How Windows Anytime Upgrade (WAU) Works windows 7 professional anytime upgrade key
The system will save your work and restart automatically. Many cheap keys sold on eBay or discount