Shipping / freight will usually be added at the end to the price. Different makes will cost more depending how far the dealer is from the RVs factory. Just like buying a car there is a shipping/ freight fee. The buyer usually pays the cost. Ours ran about $1300 we are about 500 miles from the factory. (Basically there is a per mile fee charged by the shipping company to the dealer). Having said that we knew the fee up front while making the "deal" on the trailer.
There should not be a dealer prep fee, but I am sure a few dealer charge one.