In a city of sky-high real-estate prices, gut-wrenching envy is inevitable.Keeping up with the Joneses is never easy, what with their plasma TVs and German sports cars. And it stands to reason that if we sometimes envy other people’s clothes or cars, we very much envy their homes. After all, real estate is perhaps the biggest investment most people ever make—especially here in SF, where a house costs double what you’d pay in many other cities. Naturally, people can become a little obsessed with what kind of building and neighborhood they live in.