If Sony could make Vita $250 4 years ago, they can make PSVR $300 todayEh, I don't think that's the best comparison. People expect handhelds to be rather affordable and with Nintendo as their direct competitor they were pretty much forced to go with that trend.
All gaming VR headsets aside from Sonys are definitely going to have a much larger cost of entry than $300, the Occulus is $600 and from what I've heard people are expecting the Vive to be even more expensive. I don't know how much money Sony would lose per headset if they sold them for $300, but I'd imagine it being a sum that's simply not worth it, when they'll even have the clear price advantage at $450 or so.
That being said, I must say that $300 bucks for the standalone headset would definitely take a lot of the wind out of the broader commercial potential of the Vive and Occulus as the price differential would be just too big. It would also give VR a chance to hit the mainstream a lot faster though, which is why I'm sceptical, since Sony said they'd be happy with something like 1.5 million PSVRs being sold in 2016, at $300 I'd expect the PSVR to be able to sell up to 5 million in 2016 if it actually releases in the summer and the software support isn't totally horrible.
I guess we'll find out more at GDC, it'll be interesting.