I don't understand the question - you handle the price negotiation the same regardless of whether you take delivery at the dealer or at the factory. And pay the dealer directly, not the factory. Be aware there is typically an extra fee for factory delivery services, which you "buy" as an option on the RV and pay for it as part of the RV price.
The exception would be a brand that sells factory direct, e.g. Rexhal, Lazydaze,and Born Free, or one of the custom trailer builders like Space Craft or New Horizons. You get the price direct from them, and pay direct to them.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL