Assuming this is a fairly expensive cue that the guy in ignorance gave away for free, and assuming there are no extenuating circumstances, your friend should tell the guy the real value of the cue and offer to return it, or to pay a fair price, or to sell it and give most of the proceeds back.
It will only make for hard feelings if the guy has to see his former expensive cue at league, when he had essentially given it away with no knowledge of its true value.
Sometimes *not* taking advantage of the newbies at the pool room is the right thing to do.
