Shipping will vary from company to company as well as how you want to ship. Places like JC Motors are reputable and have been used by a few people I know of to get bikes on the island. You can go to a couple of sits like U Ship (I think that is the name) and basically put an ad out there stating what you want to ship, when you want it picked up, and when you want it delivered and companies basically bid for your business at that point. So far I have received quotes from various companies going from almost $2,000 (east coast) to just under $1,000 (west coast). The tough part is finding a company that will do the job right and will not cost you more than the bike is worth. I have been working on quotes for almost two months now on RC51s and Ducatis looking coast to coast and it is a tough balance finsing one for a good deal and keeping it a good deal after shipping.
Right now there are two RC51s for sale in Hawaii, both on other islands. One has been modified to some extent and painted. I can't get straight answers on what modifications have been done unfortunately, and after about a year of asking $7,500 the seller has come down to $5,500. Shipping should be a couple hundred dollars at most. The other one is on Maui and looks to be relatively stock, I have not inquired on it however so I cannot say for certain, and he is asking $7,500.
Another option out there, and this worked for me when I bought my current bike. I posted an ad on Craigslist looking for a CBR600RR. A guy out in Texas contacted me with pretty much what I was looking for and was PCSing to the island. He sent me photos and I had a buddy look at it and give me feedback. Everything checked out, so I told the guy pending the movers breaking it, I would pretty much buy it from him. He had it shipped at no cost to anyone, and when his household goods showed up he called me brought it over, I rode it, and handed him the cash. So that is another option. One similar and dependant on your ethics, find a buddy or someone PCSing here in an area where there is a bike you want and have them ship it in their household goods and drop them some cash for their troubles and weight allowance.