Even when Monster Hunter sells modestly, it does pretty darn well.
http://www.nintendoworldreport.com/news/21100
Capcom's recent Q3 2009 financial earnings statement listed the life-to-date sales numbers for one of its biggest Wii titles, Monster Hunter Tri. Since its Japanese release on August 1 2009, the game has sold 1.15 million copies.
While this is a sizeable number, it has been speculated that Capcom is likely disappointed with Tri's sales so far, due to the wild popularity of the series in its home country. For comparison, Monster Hunter Freedom Unite for Sony's PSP also sold 1.15 million copies worldwide in the same three-quarter period, despite being released almost two years ago.
Monster Hunter Tri is on track for North American release in April 2010.