you cannot take things out of context,  Hawaii is one of the highest tax states, so the total taxes should be considered.  the train and its collateral effects (TOD, etc), will return to the state and city all if not much of the cost of the rail after it becomes operational.  further their are socials costs too, which will benefit those who use rail and live in the TODs.  these costs of quality of life, etc. are not easily measured but they provide invaluable benefits to those people and it might be the most valuable benefit arising from the rail system.