Out of the blue, there are some amazingly low unadvertised fare sales to Hawaii as low as $408 round-trip with tax included. Most of these are for spring travel (April, May and June), however fares from Dallas on United are valid for year round travel.
But only a few travel dates are available on some routes. For example, departing St. Louis on Wed June 16 for a 7-night stay. But other travel dates are over $1000 round-trip. So you must be flexible in your travel dates to get the best deals.
Chicago to Kona, however, there are lots of dates for under $500 round-trip on American.
Miami to Maui is just $401 round-trip with tax! We found seats leaving July 14 returning July 20 but others are available.
There's no telling how long these sales will last--most likely they will be gone in a flash, so don't hesitate booking them if Hawaii is in your travel plans.