PlayFront.de, where German PlayStation head Uwe Bassendowski mentioned the number in the context of the Vita's marketing.
The last update we had on Vita sales was back in May, when Sony CEO Kaz Hirai said the system sold 1.8 million units worldwide – meaning the console moved around 200K units each month in May and June. For some context, before the Nintendo 3DS received its price cut to $170 – and just days after its US launch – the then $250 handheld had sold 1.41 million units more than the Vita's current lifetime sales. As of September 2011 (one month after the price drop), the 3DS was at 6.68 million units sold worldwide – or more than triple where the Vita's selling at right now. "Yikes" is the word we'd use to describe that situation.
A strong showing of Vita games at Gamescom 2012 and the subsequent launch of said games will hopefully bolster the Vita's sales numbers. We sure aren't gonna see a price cut anytime soon.