I agree, would be hard to make an over 1,000 dollar value hold up in court. The landowner is selling far more than just an elk head. The hunter is paying for the experience of the hunt. Once he takes the elk head home, he may value the head at far more than a grand, but a criminal court is going to go with the value he would get if he sold the head and that is going to be poundage unless the bull is big enough for the collectors market.
I am no lawyer, but maybe the hunter has a civil case for the value of the hunt.
I would have handled the situation just as you said the landowner should have. Ask a few questions in a non confronting way and if you suspect laws were broken, let the warden sort it out.