World of Warcraft account value?

Well, according to the legally binding contract you signed with Blizzard Entertainment when you created your account, your account is worthless. Has no monetary value whatsoever. Selling it will, as soon as Blizzard finds out, result in the account being permanently deleted. Under the contract you signed, all ownership is Blizzard's, and you're just a licensee, so if you do manage to sell the account, Blizzard can sue you for any money you get for it. And they'll win.