The problem with your line of thought, currently the Zephyr starts at 29K and tops out at $34Kish with all the options sans any discounts/rebates. Taking a look at KBB shows that the ES350 STARTS at 34K WITHOUT a Nav system or anything that the Zephyr comes with. Even if the MkZ rises in price and they make AWD standard on it, it will still be a couple grand cheaper then the ES350.
You and I know the MkZ and Fusion are related as are the ES350 and the Camry are. But to your jo-blow consumer, they don't know better for the most part. Personally I think you'd be stupid for buying a ES350 when you can get a Camry with the same options for cheaper, yet people still buy the Lexus. Its about the image that the car portrays, not what it is underneath to most people.
I think most people are/where downright surprised by how successful the Zephyr has been, since it was pretty much beat up by everyone in on this DG, including myself. I'm seriously considering one possibility as my next car.