I take issue with this one. It's entirely possible to live frugally while living IN San Francisco. I moved here about 7 months ago and expected it to be incredibly expensive but it hasn't been the case (beyond rent).
The author mentions $15 crappy local IPAs but I've actually never found a beer for this price. There is no shortage of $7 craft beers you can buy at a brewery or bar, no shortage of Trader Joe's with the same prices as, say, Charlottesville VA.
I've found that other than rent, the prices are comparable to other places. If you get a salad delivered on postmates or uber eats or something then that's what you're paying for. That isn't SF.
I think a lot of people are living a lifestyle where they have no problem paying for stuff like a delivered salad when they can walk next door, or uber instead of taking the bus, but lots of people are walking and grocery shopping and not paying those prices.