That's unfortunate. I suspect it's a supply-and-demand thing: SF probably has more residents per capita who want to buy from farmers' markets than anywhere else

That's unfortunate. I suspect it's a supply-and-demand thing: SF probably has more residents per capita who want to buy from farmers' markets than anywhere else in the country, and so prices rise accordingly. That definitely isn't the case in most places though (not even Seattle), so I stand by my advice for everyone else.