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#21
You don't need to buy a USB or DVD. The free USB from Microsoft, made using their Media Creation Tool can do that. And unless you intend to clean install on some old machines, built for Win7 or earlier, then it's rare to find a PC that does not already have a Windows key embedded in it's bios.
So you won't need to buy any new keys either. All machines originally supplied with an OEM install of Windows 8/8.1/10/11 have a key in the bios. In a clean install of Windows 10 Setup.exe will read the embedded key and use it to activate Windows.