well i buy my license at 36-39chf max, they are recycled from "fubar" and "DOA" laptop/desktop and thus delivered sometime with a DVD copy (or a link to the ISO if not wanting to pay 1chf more for a DVD ) i got 4 of them
and they install fine no matter how many clean & re install i did, the main issue is : to trust enough a seller to buy recycled key ... (but hey i got my Genuine tag, after a phone activation, on each and all 4 got the GWX popup
)
short: for me license key is like some expensive piece of hardware: second hand