So
$200 for a basic but wireless 3dof oculus go
$400 for slightly more powerful mobile daydream with 6dof, or a tethered oculus rift, or tethered mixed reality
$500 for a Vive
Who knows how much for Santa Cruz.
Worth mentioning that Santa Cruz isn't mobile VR in the same way Oculus Go or the Lenovo Mirage Solo is mobile VR. The details are still sparse, but it's looking more and more like Santa Cruz is going to be a PC inside the headset, more comparable to Hololense, rather than mobile phone tech.