Here's a periodic update on the price of the main battery used in the Prius as sold in the UK (and, I suspect, as elsewhere), since this seems to agitate some people. Details supplied today by my local Toyota Centre (sales, service &c), Dingles of Norwich.
Last November, the price (w/o taxes and labour: ie, just battery) was GBP1321.35 (at $1.75/GBP --> $2312.36). It now (30mar2006) is GBP1530.42 ($2678.24).
This 15.8% increase is not surprising, considering how energy and materials prices have rocketed. It seems reasonable to hope that production runs and redesigns will reduce this, either by numbers falling or a static price while inflation boosts everything else. (And I have over seven years of warranty left, so whattheheck.)
BTW, prices locally vary, AIUI. (One local source, married to a Japanese, says their Japanese visitors sometimes buy car parts on visits to the UK, as prices in *.JP are so much higher.) So it's possible that in the US the $ price is higher (or lower). On top of that, unscrupulous liars could misrepresent the true price for private reasons, so be wary.
Whatever the case, those are the current UK numbers. HTH.