Delta has round-trip flights from Dallas (DFW) to Kailua (KOA) for $342 with a connection. Flights August to December. Departures on Monday, Tuesday, Wednesday, Thursday, and Saturday. Extended weekends available. Origin/Destination reversible. No Christmas dates available.
There are some flights for $298 that require an 11-hour stopover. You should probably avoid those, as 11-hours isn’t worth the $40 in savings.
A Carry-on bag and also a personal item is allowed for free on Delta. You can avoid paying for seat selection by accepting the randomly assigned seat at the gate.