those are also cheaper on ebay

Here are retial box versions:
http://www.ebay.co.uk/itm/RETAIL-WINDOWS-10-PROFESSIONAL-USB-3-0-CARD-CHIAVETTA-INSTALLAZIONE-ORIGINALE-/322431497956?hash=item4b126a36e4:g:1K0AAOSw4A5YrWqQ
http://www.ebay.co.uk/itm/Windows-10-Pro-32-64-Bit-Boite-Retail-avec-Cle-USB-/322283008217?hash=item4b099070d9:g:e8UAAOSwPCVX9AHK

many more...

Here Are for USB only:
http://www.ebay.co.uk/itm/Windows-10-Pro-On-USB-COA-Licence-Sticker-32-64bit-OS-Win10-Professional-Key-/282290730774?hash=item41b9d6b716:g:SQMAAOSwo4pYftgX

I can likely find more.
It isn't your fault, your not setting your prices to high.. it's the supplier you have. reliable cheap suppliers are a real hassle to find.