4 or 5 years ago I paid $250 round trip SFO-KOA on UA and got upgraded both ways as a gold or platinum...traveling Friday-Sunday..those were the days... Made quick weekends in the islands very easy to justify when combined with free rental car days and $100 condos on VRBO.
seems like the "good deal" CA-HI fares are now $380ish and require Tuesday/Wednesday departures and returns...and upgrades are far from guaranteed. fortunately the $100 VRBO condos seem to persist.