They imagine this place where only rich people live and work, but don't think to the next step of who does the things that rich people don't care to do...so they'll bring in poor people and then eventually complain bitterly that they either can't get what they want done at poverty wages, or that their local exclusive society is falling apart.
In short: there is no valid reason for the ultra-rich to exist. The rising tide doesn't lift all boats: it sinks the boat that have been tethered to the sea floor.