Yes, it is not uncommon to see out-of-state plates in Hawaii, albeit less common that in other states. There is a large military presence here, and that accounts for much of it, maybe most. But not all. Back when my future wife and I were graduate students at the U of Hawaii, a fellow student and her husband came here from California and had their car shipped over. Takes about six weeks, IIRC
When we went to Japan in the mid '60s courtesy of IBM my parents shipped over their gigantic Oldsmobile tunaboat. Which was a head scratcher of the first water since the fucking thing was almost too big for the road lanes and had the added disadvantage of having the steering wheel on the wrong side. I learned how to gauge whether or not it was safe to pass at age nine or so and would holler “GO GO GO” at my mom to get around slow traffic. It was probably a mercy when she finally wrecked the thing and had to drive one of the twelve OTHER vehicles my dad bought over there. At one point we had nine at one time parked around the place, including a flatbed truck that transported the current vehicle he was racing. And yet I’d go six months or more without ever being driven in a passenger car because I went all over the country on my unlimited train pass. It was an odd time in my life.