Hawaii is expensive - everything has to come in by ship...

Use a cost of living calculator:

http://nytimes.monstermoving.com/Find_A_Place/Relosmart/rs.asp

that's actually one of the more detailed ones I have seen (a quick search on google for "cost of living calculator move" caughed up a good list).

The state of Hawaii website also had lots of good stuff: http://www.state.hi.us/

I had an opportunity to work on the island of Kaua‘i and I often wonder how things would be different now if I had taken the job. Kaua‘i, BTW, is the island they used for the title scene of Jurassic Park with the big waterfall....