[ken1784]

There is a semi official comment on Japanese web site.
http://gazoo.com/nvis2/prius/qa/qa00.asp?NO=6

Unfortunately it's written in Japanese.
Following is a summary.

Comments by Masao Inoue, Chief engineer of Prius development

In battery development, the life grade is in general same as vehicle
life. Therefore, the term of a warranty of the battery for hybrids is
same as the parts used as the core of cars, such as engine and transmission.
They are "five years and 100,000km." (in Japan)

A user who owns 2000 Prius reported that his Prius ran 330,000km without any
problems in more than two years, and the battery was never to be replaced.

The cost of the battery is 128,000yen plus labor (in Japan) if you need
new battery caused by such as an accident.

Hope this helps,

 

[ken1784]

It's apparent to me that the battery life has not had a chance to reach it's full test potential yet. I would be interesting to see if Toyota or the battery manufacturer put the batteries through a test cycle to determine their lifespan. If so, is such documentation available to the general public?

Try following link...
http://john1701a.com/prius/presentation ... ion_16.htm

Additionally, what are we looking at for replacement costs (in today's dollars) if I happen to have a Prius and the batteries wear out outside of the warranty period?

Why don't you ask it Toyota Dealer to get the official price?

I'm wondering why you are so sensitive about ONLY batteries.
If I were you, I would ask engine reliability and it's replacement cost because the engine warranty is only 5 years/60,000miles compare to the battery, 8 years/100,000miles.

Ken