While it's not 2018 anymore the process is the same. You have to run comps. What is the exact same unit selling for everywhere else? Call dealers that have the exact RV you want - anywhere in the US and ask them their out the door price. You might be able to negotiate a bit from there but you'll soon get an idea where the sweet spot is. Maybe your best deal is 1500 miles away. Might be worth it to save a few grand.
This is also a negotiating tool. If an RV dealer close to home has your unit you can tell that XYZ has it for a lower price and you're willing to drive there to get it. They might match the price.