really depends on what ur tryin to do with the investment. typically the cost of a place bought in order to rent out may just pay the mortgage. buying in hawaii to sell later is a good investment because the rate of property value increase is higher than most other places.
That is just a generalization from my experience living there and looking into it myself. typically on oahu, waikiki is good for rentals, whereas throughout the island is better for the second option. Each island is different too. maui and big island are completely different in pricepoint and options too. Some good properties on kona side that can be rented out at a lower buying pricepoint.
Just some thoughts.