@glas
To my understanding, you cannot transfer your iTunes balance to person's another account. However, if you have an Apple, App Store, or iTunes gift card that has been redeemed but unused, you can request to have the balance placed back into the card. The card would then be worth something in a trade. It depends on who you are buying from and what you are buying.
I sell sex products and would be willing to accept it.
@Datamine
Do you have a use for it? You can use it to pay for an Apple TV subscription, which is sort of like Netflix. It's got some decent movies and shows.