Usually 5% return on cap rate is already considered pretty good on Oahu. For those looking for higher return, it might be quite difficult.
If you have a million dollar and would like to get better rental return, you can consider buying 2 properties instead of 1 property to product a better rental return. However if you are looking for a comfortable home for your future use, you may want to get a higher price home for personal enjoyment because in that case you are not just looking for rental return.