I found about 18% is average. I would not take a deal less than that. Some get more, some slightly less, but no way would I take one for less than 18% with no trade in. Other dealers will deal and some are willing to work on shipping it to you. I drove about 350 miles to pick mine up, it had a leak they and Airstream missed (go figure
) and the dealer paid to have it shipped to me after it was supposedly fixed (which it wasn't, but that's a whole nuther thread).
Bottom line don't think that you are limited to dealers in your own area or state. I went two states over for mine and got what I consider a honey of a deal and I had a trade.