Windows 10 Key Activation

Just bought a W10Pro key for my Bootcamp installation through Parallels. Only paid $12 and change. Key worked fine so far, though I have heard rumblings of MS rejecting such keys even after activating Windows with them. Cross fingers.
You don't "need" to activate Win10 in allot of cases. As it will work without the key with limitation you may not even care about. Just give it a quick google. I've known lots of people that never bothered because the limitations have no effect for them.