In my years of negotiating deals on machinery for industrial bookmaking and printing machines I found that most sellers respond well when you treat them as a valued supplier and not in an adversarial way. Find a salesperson that you are comfortable with and then just say to them "what is the best price you can offer me and we still remain friends?" Most of the time they will enjoy the opportunity to work with someone not trying to beat them to death. This assumes your salesperson is a good one.
Times are pretty good in the new RV business. Traditionally you can expect 28% off list price. Maybe less than that today.