Quote:Microsoft charges $200 for a Windows 10 Professional product key. But, with a quick search online, you can find websites promising Windows 10 Pro keys for $12 or even less. That’s a huge saving—but don’t fall for it.

Why Are They So Cheap?

The websites selling cheap Windows 10 and Windows 7 keys aren’t getting legitimate retail keys straight from Microsoft.

Some of these keys just come from other countries where Windows licenses are cheaper. These are referred to as “gray market” keys. They may be legitimate, but they were sold for cheaper in other countries. For example, Windows keys were once much cheaper in China.

Other keys could have been purchased with stolen credit card numbers. A criminal acquires some credit card numbers, purchases a bunch of Windows keys online, and sells them through third-party websites at a cut rate. When the credit cards are reported as stolen and the chargebacks occur, Microsoft deactivates the keys, and those Windows installations are no longer activated—but the criminal gets away with the money people paid for them.

Full reading: https://www.howtogeek.com/392080/cheap-windows-10-keys-do-they-work/