A quick google search on jones act and hawaii reveals this page hosted by International Longshore and Warehouse Union (ILWU)

https://www.ilwulocal142.org/news-item/jones-act-fact-vs-myt...

Few things listed there are clearly false.

"Myth #2: The Jones Act Raises Prices for Hawai‘i Residents.

However, a comprehensive 2020 study by Reeve & Associates and TZ Economics found that this is simply not true.

Their survey compared the prices of 200 consumer goods—including groceries, household items, clothing, and automobiles—at major retailers like Costco, Home Depot, Target, and Walmart in both Honolulu and Los Angeles. The results showed that prices in Hawai‘i were, on average, only 0.5% higher than on the mainland, a negligible difference that cannot be attributed to the Jones Act alone."

As a frequent visitor to Oahu, i stop by Costco on the way from the airport and i can see that most consumables including milk and meat is 30-50% more expensive than at Northern California Costco. This is representative across local supermarkets as well.

So its seems that this union is trying to minimise the impact of shipping on costs of everyday goods

Critics dismiss this study as bogus:

https://www.grassrootinstitute.org/2020/07/shipping-industry...

"using online prices to compare food prices at Hawaii versus Los Angeles stores is problematic. A visit today to the Keeaumoku Street Walmart showed an 18-ounce box of Cheerios selling for $4.26, before tax, versus $3.64 for its listed online price, and a four-pack of 5-ounce cans of albacore tuna for $8.43 versus $6.74 online."

That is actually true, Keamoku Walmart does not pricematch to their online prices and the only way to get those prices is to place an pickup order and wait for several hours to pick up at those prices.

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