That’s a short question. Too bad there isn’t a short answer.
Anything not produced on Molokai (that means almost everything) is expensive by mainland U.S. standards. Most of the items in the stores have to be shipped from their point of manufacture to Honolulu, unloaded, reloaded on a barge and shipped to Molokai. This ups the retail price by 20 to 100%.
On the other hand, room rates are, in most cases, lower than like accommodations on the other islands. You can have a nice condo that sleeps 4 comfortably for around $125 a night. Less per night for stays of a week or more. Likewise, dining out is no more expensive than at other Hawai’i visitor destinations.