Depends on your goals in life. $7,000 is definitely doable. But I don't want to live in an RV. Indeed, I want to live in a walkable neighborhood with groceries, low crime, and easily accessible entertainment.

The site probably isn't a convincing case for a general audience. Which is a real pity, because a lifestyle of $10,000 to $12,000 a year is very doable, even for a single person, even in the Bay Area, even with regular outings and entertainment, and even with flushable toilets.