They are just trolling for those sweet sweet Silicon Valley dollars. No one who knows anything about CB750s would pay those prices for those bikes, but there's guys making those sweet Google bux with cash burning a hole in their pocket who might think one of these looks like a cool way to spend it.
SF Craigslist is full of flippers who will take whatever hipster trend is handy, and cash in on it. They probably buy these bikes off craigslist in another less hipster area of CA throw on a low effort "cafe" build, and they're flipping them for at least 5x what they have in them.