For the 2016 Softail Slim S in a color other than black, the MSRP is $18899. Invoice would be about $15120. Freight is $390 and is not included in the MSRP or subject to markup. In other words, it's a straight pass through charge from the manufacturer, and it is a legitimate charge. On the other hand, other charges like dealer prep are pure hogwash, since H-D pays the dealers to do the minor amount of "prep" required, like installing the Maxi fuse and setting up the security system, installing or adjusting mirrors and any other parts not actually installed at the assembly plant, etc. Document or "doc" fees are also questionable, since preparing the sales documents is a normal cost of doing business. The folks at Home Depot don't charge you a separate "doc" fee for preparing and printing an invoice for your purchase, do they?
Anyhow, once you've figured out what the dealers invoice cost is, you still haven't determined his true final cost. I assume they still have a holdback allowance just like the car dealers, but can't state that as fact. If they do, that is usually a certain percentage of the MSRP that the factory "holds back" until the vehicle is actually reported sold by the dealer, and then paid in a lump sum for all vehicles sold either quarterly or semi-annually. In the car business a common holdback is 3%. Then you have various dealer sales incentives that can kick in additional profits. You probably won't see that on a new Harley early in the model year, but might toward the end of the model year. The problem is the public never really knows if such incentives are in effect, or how much they might be. On a totally new model, I wouldn't expect much of a discount if any this early in the model year, but there is no harm in asking. The worst that can happen is they say no.
Jerry