Gamasutra says that World of Warcraft has sold approximately 8.6 million units, reporting data from the NPD group that adds further perspective to our understanding of the huge success of Blizzard's MMORPG that boasted 11.5 million subscribers as of December. While the game has not sold as many copies as there are subscribers (update: according to Dagok, these are US figures only), NPD has rolled up data on multiple SKUs of the game and its expansion packs to come to that 8.6 million figure, and Gamasutra guesstimates that this could amount to about $258 million in sales, a staggering sum, except when compared to subscription revenue, which would pass that in two months if all 11.5 million players were paying a full $15.00 a month.