Therefore it is NOT a prize!

It is a gift.
Now, that's interesting. Technically, it's not a prize, because he didn't win it. It is indeed more a gift, given to him by Keysight at good will. How about taxes on gifts, are there any in the US? I've tried to do a google search on it and that seems to be the case. BUT:
Who pays the gift tax?
The donor is generally responsible for paying the gift tax. Under special arrangements the donee may agree to pay the tax instead. Please visit with your tax professional if you are considering this type of arrangement. (from some IRS website)
So, if I understand this correct, Keysight ist responsible to pay the gift tax on the scope, not Carlos? Would be even better than the contest prize, lol...

And what's up with David K. (second place, behind Nilu but ahead of Carlos), will he also get this 6000X "gift", though he got almost 50% of his votes (for some, cough, unknown mysterious reasons) removed?