It's been said numerous times...
Platform (US release) MSRP in Japan/US: actual JPY/USD exchange rate -> exchange rate based on comparison of prices (plus percentage that Nintendo adds to price of US dollar in yens):
DS Lite (Jun 2006) ¥16800/$130: ¥114.63 -> ¥129.23 (plus 12.7%)
DSi (Apr 2009) ¥18900/$170: ¥98.89 -> ¥111.18 (plus 12.4%)
DSi XL (Mar 2010) ¥20000/$190: ¥90.68 -> ¥105.26 (plus 16.1%)
Based on current exchange rate of ¥84.47 plus 16% that'd translate price of ¥25000 into $255. It's up to debate how much will exchange rates fluctuate in Oct 2010 - Mar 2011, it they won't you'll get 3DS in US for $250, if dollar will fall (it actually didn't fall that mach in Oct 2009 - Mar 2010), then expect $270 price tag plus some bundled game or a movie to make 3DS more attractive.
