Wondering type of air deals people have been able to get for a RT airfare for LAX - Maui - Oahu/Kauai in late August. Traveling for approx 7-10 days total, with a 2/3day stop in Oahu/Kauai either before or after Maui.
The best way I know to find the cheapest flights every time (especially when flying domestically) is to use the Google ITA matrix.
I picked completely arbitrary, late August dates using the info you gave and a multi-stop ticket is coming out to $724 dollars to visit those two islands and then return.
I'm sure if you searched each trip as a one-way and found the cheapest day in a "calendar view" of flights on the ITA matrix, you can find cheaper.
If you want to learn how to use the ITA Matrix (its fantastic and not that hard to use), check out this video we created. It's helped a lot of people already!
Honestly, I'd either just keep checking back for sales or sign up for airfarewatchdog.com alerts. I just got an alert today about flights to and from NYC on jetblue for $30 each way! It's gone now, but it would've been only $64 round trip for me to fly from Los Angeles International AirportJohn F. Kennedy International Airport and back!
Here's a pic of the search I made:
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if you try thanksgiving period, which is kinda known as low season in hawaii, you'll probably have better prices :)