Since this thread orginated in the Hawaii forum, we'll need some more information here in Travel Buzz. The bottom line is that Hawaii is a very unique place, and is truly one of a kind. You'll have to tell us what else is important to you to help us hone in on your preferences.

I'm not sure where the non-stops go from SFO, but there are many options. Six hours from SFO on a non-stop flight will include all of North America and all or most of Central America and some of the Caribbean.

Is a tropical climate a prerequisite? That would eliminate quite a number of lovely, remote, inexpensive beaches in the USA or Canada. But since I"m not clear on that point yet, I'll make my suggestions:

-If safety, cleanliness, cost and solitude are what you're seeking, the Pacific Northwest/Oregon and Washington State would meet the requirements beautifully. Depoe Bay is not far from Portland, or Vancouver Island outside of Seattle. Although you're looking to fly, a lovely drive up the "Lost Coast" to Brookings (or beyond) from SF is something every Californian should do at least once. As a part-timer in the PNW area, I consider it vastly underrated as a travel destination. The coastlines are simply stunning and a crowded beach means that you can see 6 or 8 people if you look in both directions.
-If the hip Hawaii vibe- Oxnard or Ventura are affordable options just outside of Santa Barbara
-In So. Cal.- Laguna Beach... not too private on the beach, but gorgeous coastlines and there's plenty to do. Your ocean view price point might be possible in the off season.
-In Mexico- Loreto is still relatively uncrowded, very inexpensive, and has some interesting activities in the Gulf of California (swim with the sea lions, whale watching, snorkeling, Old Spanish Missions, cave paintings). There's a direct flight from LAX.