Looking at a Geringhoff Rota-Disc corn head on auction. I'm not very familiar with then but we have a few of them running around us. I've heard they're good heads but have been told they're very expensive to go through when the time comes to start replacing things. Had a salesman tell me about $3,000/row to completely go through one. Wondering if that's true or not...? Anyone have any other experience with them, good or bad?