I don't know. One of my friends is bat**** insane when it comes to rpgs, both J and W, and has picked up FFXIII day one, and I've yet to meet a 'JRPG fan' as you describe it, outside of gaming forums. Then again, my personal experience doesn't mean much, but those numbers must come from some people, and trust me, they can't be all JRPG hardcore fans.
EDIT : Also, about Dragon Age, I'm pretty sure I saw solid datas that put its sales (a lot of time ago, by the way) at over 2 millions... at least.