This is the same question I had in Sept '06. After much investigation we found it was cheaper to ship our own bikes (CBR1100XX and a VFR800) ex Brisbane to Vancouver for a short 9 week 18000km ride across Canada and the States. Cost per bike sea freight return was approx. $3400.00 AUD, with us crating and uncrating either end ourselves. A friend has since bought a pre '88 Gold Wing in the States, rode it around for several months then shipped it home and sold it for a profit. Anything after an '88 model is a lot more drama for rego. This might be worth a go!
Enjoy the trip it is fantastic riding country, particularly the Rockies.
Hope this helps
Feb 2014, currently travelling the America's on a Tiger 800XC
Live every day like it's your last, one day you'll get it right!!!