I feel sorry for the tourists who -- when surrounded by the incredible food bounty of the Hawaiian islands -- head to Walmart or Costco and buy the same stuff they already get at home.
Bringing raw ingredients to Hawaii is sort of like saying, "I'm traveling to Germany. I'm going to pack as much beer as I can carry into my checked baggage."
Or, "Off to Italy. I'm going to pack all the Tombstone frozen pizza I can!"
Or, "Heading to China -- with a 50-pound sack of rice!"
I know some people who simply don't care what they eat. "It all ends up the same place." So they live on a diet of packaged ramen, Chef Boyardee, Hot Pockets and fast food. If someone like that goes on vacation, then, sure, why not just bring the cheapest stuff possible?
Instead, I'd go straight to a small, local market. Buy local fish, local produce, and Lum's Char Siu sauce (they should pay me for all the times I mention them). I'd buy some frozen coconut cream (every store has this), panko flakes and make some coconut mahi. Get some mac-nut pesto at a farmer's market to spoon over the mahi.
The best tomato I've ever eaten grows in Hawaii. The best fish, crab and lobster I've ever eaten grows in Hawaii. (Yes, crab and lobster at the aqua farm -- pumping water from 12,000 feet down for the perfect cold-water environment.) Best avocados. Best guava. Best papaya. Best mangos. Best citrus. And even for the things where Hawaii isn't the best (beef, for instance) it's still WAY better than most of the beef found on the mainland. It's not A5 Kobe. But it's better than what can be found at Piggly Wiggly.