Unlike cars, there is no standard for MSRP. Often, dealers make up their own MSRP and then give a big discount. And you might have thought car salesmen are bad!
If you are looking to buy a new RV, check the Internet (RV Trader, PPL, etc.) to see what dealers are asking for the RV you are interested in buying. This will give you an idea of the usual pricing. However, as with buying new cars, be prepared to negotiate a lower price than the listed price.