Dealers always buy at wholesale book and sell as close to retail book value as they can get. They may allow more than wholesale as a trade-in, but you can be sure any additional allowance was offset in the selling price. That means the gross mark-up is the difference between wholesale & retail. As a gross generalization, that about 1/3 the NADA retail book value. Net mark-up is a whole different story, so the dealer has to cover his overhead, repairs, sales commission, the PDI, etc.
Former owner of 2004 American Tradition and several other RVs
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC