You pay the OEM once, for a Windows 7 key, and then you run on that -- because it keeps working, with Microsoft's implicit authorization -- for the next 15+ yea

You pay the OEM once, for a Windows 7 key, and then you run on that -- because it keeps working, with Microsoft's implicit authorization -- for the next 15+ years. They 100% would not let you do that if they cared to charge for Windows like they did in the pre-Windows 8 days when Windows was the product and not the user's data.