There is also a huge difference in price expectations between men and women (IME, of course there are differences for any gender) - most men I know expect to pay £5-£15 for a haircut, whereas most women I know expect to pay between £30-75 for a haircut.
At a salon you can get a restyle, shampoo, blow dry and all that stuff, which obviously adds to the time and cost, but even for a very basic trim you're looking at at least twice the cost at a salon vs a barber.
Personally, I cut my own hair with a set of Wahl clippers I've had for something like 20 (!) years. This obviously means I'm restricted to a buzz cut, but I think it suits me and has doubtless saved me a lot of money over the years :)
With the California housing crisis, this is solved by the fact that those folks don't live in SF. Many of them commute over an hour each way for those jobs. It's sort of a problem for us...
I'm not sure I would go to a robot arm.
I bet there are places in California that are similar. Who cuts the hair of the guys who clean the streets and empty the bins? I don't suppose they can afford $65 for a haircut..