This is especially the case when you fly Business or First class to/through the islands.
As an example, EWR-OGG on random dates in August in J $4,370.90.
On the same dates, EWR-HNL in J is $2,704.28.
By not breaking up the HNL-OGG interisland flight off, that additional interisland round-trip is $1,662!!
The most expensive round-trip first class interisland ticket on HA is $218, so you'd be paying CO an 800% premium by booking it online their website.
I like flying interisland in F; you're 1st one on/off as are your bags... and you can hang out in their lounges while waiting for your flight (which comes in handy in places like KOA where the gate area is outdoors ...which can be very hot at times in the summer. I'd much rather be sipping guava juice in an airconditioned lounge
) However, unless you have money to burn, $1,662 just isn't worth the 30-minute or so each-way flight ...and even a non-discounted $218 makes it debateable.