Flying OAK - OGG - SFO, all in F. AS there, VX back. Fare was ~$1000 RT. Cheapest all-F (not mixed cabin) on UA for the same dates is >$2000 RT from bay area to OGG.
It really depends on the dates and routes. Although the cheapest I've ever seen a weekend bay area - hawaii first class round trip on UA is about $1300 in F.