Lifted from Gaming Age:
"Yesterday in Japan, Square held a Final Fantasy X sale commemoration event was at the Virgin Megastore at the Shinjuku branch in Tokyo. During the event, it was announced that 2,140,000 copies of the game were already sold through pre-order, and another estimated 1,500,000 would be sold within the first day or so."
Maybe the 10 million mark is a possibility.