SwamiSalami, thank you for confiding with us that you let a soccer mom beat you. I will treat your secret with the utmost respect!
I have been trying to find numbers on the Prius since before I found this site. According to HowStuffWorks, Prius batteries have come down from $5,500 to $2,400 (1) HSW does not date their articles, but their most recent source is June 25, 2009, so that is a reduction of 56% in nine years, or 6% a year. They also stated that "Honda has cut its battery replacement price from $3,400 to $1,968." (2) In an article about Lithium-ion batteries, Green Car Report stated "the rate of performance increase has averaged 6 to 8 percent a year."
I finally found my numbers! "Toyota's out-of-warranty battery replacement rate has plummeted from about 1 percent for the first generation Prius to 0.003 percent for the second generation." (2)
I am also curious which hybrid the brother had. People have very different experiences with the same make and model depending on their attitudes, driving habits, and maintenance. Green Car Reports included the Honda CR-Z and Insight in "Five New 2012 Hybrid Cars To Consider Steering Clear Of." (4) One of the others is a BMW and two are Lexus...es.
(1)
HowStuffWorks "Hybrid Battery Replacement Cost"
(2)
HowStuffWorks "5 Ways Hybrid Battery Packs are Being Improved"
(3)
How Much And How Fast Will Electric-Car Battery Costs Fall?
(4)
Five New 2012 Hybrid Cars To Consider Steering Clear Of