Years back I sold new cars. The dealer cost included an admin fee and pre delivery inspection, keep in mind this was 40 years back and that cost was $1000. I'm thinking the dealers do the same today but adjusted for inflation, lol.
Now for my offer for the new boat, I bought it in 2014 and was the end of the year so the dealer wanted to clear out his inventory. I traded in an older boat with a bad motor. As I recall I offered about %10 off his asking price and it was already discounted due to end of year. He accepted and the rest is history. I looked at the new boat as a once in a life time purchase.