Hi RK,
I am Sumit, an Independent Advisor and a 3 year Windows Insider MVP here to help.
These are likely volume licenses that are intended for the business environment. As soon as Microsoft detects they are abused, the keys are disabled. To summarize, this is illegal and does not come with warranties. As compared to Store, Microsoft provides full buyer protection.
Via https://www.microsoft.com/en-us/howtotell/Shop....
Beware of Product Keys Sold Separately
With the exception of Product Key Cards (PKC’s) distributed with COA’s, Microsoft does not distribute products keys as standalone products. If you see a listing on an auction site, online classified ad, or other online page advertising product keys for sale, it’s a good indication that the keys are likely stolen or counterfeit. If you were to purchase and use a stolen or counterfeit product key to activate Windows installed on your PC, the key may not work for activation, may already be in use on another PC, or it might be blocked from use later by Microsoft when the key is reported stolen.