To answer your question, I would first line-up your requirements to the current market. There's nearly 150 homes available in Bethesda, Chevy Chase and Potomac priced over $2M. As with any home, it's worth what a buyer is willing to pay. There's so much on the market right now, you may well find equally "great" homes that meet your needs for quite a bit less.
Here's some basic stats on upper bracket homes in Potomac - http://mocorealestate.com/2009/04/01/the-lure-of-bargains-in
I hope that that helps.