The airfare was the biggest chunk.. and the incidental costs at the hotels in Hawaii. Hawaii overall was a big chunk of the rest of the costs.
My airfare = $2100 (high season)
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Hotel costs averaged $47/night but I used points or points+cash at hotels in Hawaii and Saipan, so that kept costs down.
For the western Pacific part of the trip, I spent under $800 in a week and $200 of that was for diving.