It depends on the local market and the dealer. Something between 20 and 30% below MSRP is often negotiable, for brands sold through dealers.
For direct sales from a factory, the price is sometimes negotiable for what might be in stock, but not always negotiable for built to order, but when there are no dealers MSRP doesn't really have a meaning.
Look at prices offered by discount outlets like RV Direct, use that as a bargaining goal with working with dealers selling the same thing.
Tom Test
Itasca Spirit 29B