Remember, you do not really know how they bought the keys since it could be someone trying to get rid of a product as how often do people really pay sticker price for anything.
And just for your information, I am a Microsoft shareholder for longer than most people so I know how they make money. It all depends on the distribution channel on where someone gets their stuff which might not always be someone buying a volume license key.
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And using your Ferrari example, I know for a fact that many people have bought BMW's at cost since there is something known as MSRP (Manufacturers Suggested Retail Price) and what prices it's allowed to be sold at. Some manufacturers have something called MAP (Minimal Advertised Price) which is what they agreed not to sell under. Louis Vuitton and Rolex are two examples of things that never sells below sticker price as it's their policy but Omega on the other hand can often be bought under the MSRP.
But anyways, using your link, it has been said that it's Volume Licenses that are the ones that are the ones with problems as this is what I get with what they recommended as a way to check using slmgr -dli:
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People can sell things for anything they want to and there is virtually no risk since it's not like the money will be lost as this is protected by Regulation Z of the US Truth in Lending Act should something go wrong.