Looking at the Xbox360 sales of Call of Duty 3, they stand around 1.5 million. The sales ratio of America to PAL regions is about 2.8. But remember that the Xbox360 has sold nearly half as many consoles in PAL regions as in the United States, while the PS2 sales ratio between the US and PAL is nearly 1 (around 1.06 to be exact). Once again, sales of CoD3 in the US, for the PS2, are around 677,837 copies sold. The assumption is that PAL regions, which in games like Call of Duty: Finest Hour showed sales nearly equal to that of American sales, should also buy this game to the same degree. Assuming that it sells around 50,000 copies less in PAL regions compared to American sales, that would put the total sales of this game at around 1.3 million copies sold. From this I still this stock is undervalued.
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Sources:
http://vgchartz.com/worldtotals.php?name=call+of+&console=&publisher=&sort=Total
http://vgchartz.com/worldcons.php
http://vgchartz.com/aweekly.php?page=3&date=39236