550k global monthly searches. Someone contacted me to buy it.
I agree with the others concerning the trademark issues. There is no way you will be able to prevail with a legal argument that you were in good faith and wanted to use this name for something unrelated to YouTube.
However, if someone has contacted you to buy it... you could mention the possible TM issues to the buyer and if they are still interested, maybe you can sell it quickly and thus get rid of the problem. I don't think the sale would be underhanded towards the buyer as long as you make them aware of the situation.
On the other hand, I do not know enough about IP law to say whether you might still be held liable for trademark infringement if it was you who originally registered the domain, which it appears that it was.
Regarding price, which I think was your real question, I'd say be happy if you are able to sell it for whatever price the buyer is willing to offer (after you have mentioned the TM issues). Sorry. Although initially disappointing, a low price might be a blessing in disguise as it will then be more difficult for a complainant to argue that you registered the domain in order to try to profit on the trademark infringement. In fact, I think I would be concerned about making any money on this domain. Maybe you can pass it on for reg fee?
Remember that although the domain has not been discovered by YouTube yet, as soon as it is out of your hands, it might be brought to YouTube's attention and then you cannot control what happens.
Good luck no matter what you decide.
Update:
On second thought my advice is to just cancel this domain. I see no possible uses for it outside of trademark infringement, and if that is what your buyer wants to do, let them register their own domain and keep yourself out of trouble.