Well, I for one would love to hear about your discoveries...
Okay, first for the items I brought up in my post -
Housing - We never considered purchasing a house since single family dwellings are typically 30 to 50% higher in cost than condos of similar size. It makes sense because (while building costs are higher) the main cost of Paradise is land (except on the Big Island, they aren't making any more of it.)
Rock Fever - It's a real phenomenon that folks from the mainland can't get used to just how small the Islands are. If Oahu were square, it would be less than 25 X 25 miles. To avoid Rock Fever, simply leave the Islands once a year or so. Once you know you can get off the "rock", Rock Fever usually goes away.
Food and other consumables - We use Costco or Sams for most food items and other consumables. While the costs are higher in HI than on the mainland, they are much lower than at regular stores in HI. Stuff like CDs, books, clothes, furniture, etc. we purchase at 2nd hand stores. We furnished a 3 br condo with amazing Island style furniture for less than $2K. The stuff came from hotels which were updating and we had our choice between dozens of the same table and hundreds of the same lamp. We got to pick out a near perfect "whatever" and bought it for a song.
Traffic is a real pain on Oahu - much more so than any of the other Islands. But, like most cities, Honolulu has rush hours and we simply avoid them. We make Dr. apps. for 11:00AM instead of 9:00AM. We eat dinner out in our neighborhood or else eat lunch in the "city." Prices are lower that way as well. We now know a lot of hole-in-the wall eateries that are not that much more expensive than mainland restaurants. Eating "local" is relatively inexpensive and delicious.
Travel distance to family/friends - We tell folks the planes go both ways. Ya'll come! So we do have visitors AND we travel around the mainland when we are back. As long as the planes fly and we don't run out of money, it's not that big a deal to be 5000 miles from where we once lived. We ARE getting to the point of considering traveling 1st class, but so far, we have not.
Movies - Actually, movies are not that much more expensive in Paradise than on the mainland, but we have found a 20 seat theater (leather recliners) that charges seniors $4 for movies - often just off-first run and sometimes 2 or 3 feature retrospectives - bring your own popcorn and drinks OR your lunch!
Cars - Because the Islands are small, there is generally less driving required. Most folks in HI are much less concerned about what you drive than on they are on the mainland. There is much less "keeping up with the Joneses" on almost every front. Our cars are 16 years old and no one cares. If we couldn't afford to drive, there is an excellent bus service that has fantastic senior rates (IIRC, maybe $60 for a 2 year pass??)
My original point, of course, was that cost-of-living comparisons that you see in all the "books" and magazines and on the Web do not address how folks actually live. With some sacrifices, one can adapt and thrive. I'm sure it's that way whether you live in HI or SoCal or PNW or Boulder Co. There are always a few bargains and usually adequate "substitutes" for what you have become used to in rural Ohio or Mississippi or Nebraska. As always, YMMV.