That's a ridiculous price! Hawaiian Air one way fares between HNL and OGG are pricing out at $39 + taxes, for sample travel date of 7/11 and 7/12. To pay $320 + 50k AMEX points is a terrible deal. Unfortunately, if you booked already, the cancellation fees can be quite expensive.
That's $320 for four tix, or $80 each. If she meant r/t then it's a very good deal as now the cost seems to be $109 r/t.
Now here's a bad deal:
$756.28 Avg. Price/Adult $825.20 Avg. Total Price/Adult »
Choose this Departure » Fri, Jul 24 Northwest Airlines 5016 Equipment: 717 Booking class: Y/Coach
Fare basis code: Y
Depart: 5:00 AM Honolulu/Oahu, HI (HNL) Meal: None
Arrive: 5:36 AM Kahului/Maui, HI (OGG) Approx. flight miles: 101
Duration: 0 hr 36 min Operated by Hawaiian Airlines
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Choose this Return » Fri, Jul 31 Northwest Airlines 5029 Equipment: 717 Booking class: Y/Coach
Fare basis code: Y
Depart: 6:04 AM Kahului/Maui, HI (OGG) Meal: None
Arrive: 6:38 AM Honolulu/Oahu, HI (HNL) Approx. flight miles: 101
Duration: 0 hr 34 min Operated by Hawaiian Airlines