Doubt this has anything to do with WN (where you can't even get back to GRR without separate tickets). You can find fares in the $800 - $900 range from places as remote as IMT. I checked before and after fare filings on ExpertFlyer for GRR-OGG on DL and there have been absolutely no changes. Cheapest main-cabin fares remain VRYNLOML fares for $873 roundtrip. Simply altering your departure day by a day or two can have a dramatic effect on fares available as the cheaper fares have Mon-Thu departure requirements. If you were looking a peak seasonal trips with Fri-Sun departures, you won't find anything for less than about $1200 and that still remains true.