It's a supplementary platform to the PlayStation ecosystem, so it doesn't stand alone like a primary machine (say, PS4) does. 40k is a win in that sense, because it's 40k more instruments in the Vita/PS4 ecosystem. And that's just the US.
Worldwide, you're looking at over 100k.
The thing sells games and services, while making PS4 and Vita ownership even more appealing. I do not have a PSTV, but I intend on getting one.







