First of all, the current wholesale price for the battery is about $1000 and in 5 to 10 years better batteries will be less expensive. There will also be an active market in salvaged batteries as there is now for the Prius (they sell for a little more than $500 on Ebay) as the number of TCHs on the road grows.

There are many other expensive parts on cars that wear out (eg. automatic transmissions) and cost more than a replacement battery so stop worrying and enjoy your car.

JeffD