Where to buy Windows 10 New license? Online store or Microsoft Store?

Windows Desktop Windows 10
1

I have got one new client who seems to have still using a few Windows 7 PCs in his environment. Good for him he has decided to upgrade all those PC to Windows 10. All of his windows 7 is a Professional version so it needs to upgrade them to Windows 10 Professional. Most likely I will be doing destructive upgrades on these systems so I can do a clean install of Windows 10. I planning to buy from eBay or Newegg or direct from Microsoft Store. But from my experience most of the vendors in eBay and Newegg selling the license for a cheaper price.

Windows 10 on Newegg
Windows 10 on Newegg1344×614 102 KB
Windows 10 on Ebay
Windows 10 on Ebay1036×535 74.3 KB

Now here is my clarification, Does anyone used these inexpensive licenses? Any pitfalls to be aware of? and Does an “upgrade” license allow you to do a clean install of windows 10 as long as you have the windows 7 license key?

Thanks for taking the time.

Happy weekends

2

Hello @Addison

Here is the answer of your question.
https://www.microsoft.com/en-us/licensing/how-to-buy/how-to-buy