Call me crazy, but I'd expect folks that purchase houses such as these are in a position to pay cash and don't take out a mortgage on them? Now 3-4 million range, I see celebs, etc. losing their homes when their star falls. At this level, I don't think anyone who would qualify would need/want one?
At the much cherished 400:1 ratio (need $400 to generate $1 month), you'd need ~$177 million. Interesting how that's actually not that much more than the cost of the home (relatively speaking). I wonder if that's universal (if you have the just over the value of your home in investments, it'll generate enough to make the monthly mortgage payment? Something to run the numbers on later).