Gotta think of the bigger picture. Not only is there the mileage-to-payback for the extra cost of the vehicle it's self, but there is also a host of specialized repair and service equipment required, and even more important is the need for trained technicians to service these techno-monsters. Couple that with the financial troubles most towns and schools are in at the moment, and they're lucky to be able to maintain the dinosaurs they run now.
It should come... It will come. But it's kinda in the realm of solar panels at the moment.
In the long run I'm not convinced that the stuff we make these batteries out of will be a positive trade-off for the emissions once they start winding up in junkyards and landfills.