Sales decreased 14.5% year-on-year (a 10% decrease on a constant currency basis) to 118.0 billion yen (1,493 million U.S. dollars). This decrease was primarily due to lower sales of hardware and software of the PSP (PlayStation Portable) and PlayStation 3, partially offset by the contribution of the PlayStation Vita introduced from December 2011.
Which means that while it is not selling in great numbers, the Vita makes Sony money, something that the PSP and PS3 are failing to do. Around a third of the actual loss is due to the weak Yen and Sony losing money when it sends the money back home. But with sales down 10% overall, Sony needs to sell the Vita for as much as it can, it needs money more than it needs big (loss-making) sales figures.
Of course, publishers and developers (both first- and third-party) would rather have lots of Vita owners buying their games. But, in the grand scheme of things any long-standing developer knows that once the early adopters have arrived, it will be a slow curve upward, especially in such a crowded market.
Nintendo could do the 3DS price cut because they only have consoles to worry about, while Sony's empire is crumbling in many places, making decisions like that far more complicated.