They know that these books would be purchased by a niche market overseas, even among people who do play FF games. Not everyone who likes FF is going to buy them.
They've already made their money on them in Japan, so they're not concerned about a small profit, even though they wouldn't be footing the costs of the translations, paper, etc. Their concern is potential investors who don't know the franchise and don't care about anything but its money-earning potential looking at those minimal sales for the books and taking them as a reflection of the FF brand's overseas viability -- and, thus, as an indication of Square Enix's own lucrativeness.
