The PS4 Headset is $400. You're also going to need at least the PS4 Camera, and for full game functionality you'll need a pair of motion controllers, so you're really looking at more like $500.Took the kids by Best Buy yesterday.
They were demo'ing both the Oculus Rift and the Playstation VR.
My older boy tried out the Oculus Rift, and he, myself, and my daughter each tried a different game demo on the Playstation VR. My son tried out Batman Arkham, my daughter tried a carnival game, and I did a space flight game.
I was actually impressed in how well it worked. So it looks like the kids will be getting the Playstation VR for Christmas.
As for Oculus Rift, not so sure about that, as it's $200 more than the Playstation VR, plus it has some beefy hardware requirements, and I'm not 100% certain the computers we have are worthy of it, have to check, as the demo person gave me a card of the website that you can check out your hardware on.
Don't forget that for the full experience of Oculus you're going to need to spend an additional $200 on the Oculus controllers.
As far as hardware, unless you have a gaming PC, odds are it's not going to be able to run it. If you don't have a $350+ dedicated graphics card, then odds are you won't be able to use it. Also, the HTC Vive is another option.