1 gallon of milk costs $6.00 here.
Perhaps there is only 1 cow on the island.
I will not pay for bottled water, costs about a dollar for a pint. No one complains about this outrageous ripoff about water and milk, tho.

1 gallon of regular gasoline costs $2.25 on Oahu. On Maui it is $2.50. Extra barge charge.
Hawai'ians pay 58 cents tax per gallon.

There are 2 oil refineries on Oahu.
(No new oil refinery has been built in the United States since 1976 causing a bottle-neck. Demand has outstripped the infrastructure to supply it.)
If one 100,000 barrels per day refinery is shutdown for a week within a close by region, you will see a spike in gasoline prices. 10 cents.
There are not enough VLCC tankers to ship all the oil produced now, and insurance rates for these ships increases as war and terroism increases.

A war in the Middle East ALWAYS drives up the price of a barrel of crude oil.

The Venezuelan oil workers went on strike for 1 year! The Nigerians attack oil installations. The North Sea is drying up. The Gulf of Mexico oil reserviors are way deep now, and needs fancy expensive rigs to suck it up.

China cannot produce enough oil to supply the demand of her exploding new rich economy and all the new cars that have displaced the bicycles. She is now the 2nd largest consumer of oil after the USA. (I see a conflict brewing here)

The Iraq oil fields are still not producing to pre-war levels. No security, no money to replace parts.

Did I mention taxes, or the situation in the USA where every state has different regulations concerning gasoline formulations to meet the plethora of all the different environmental laws unique to each State?
Please forgive me. Pant...pant...