Well the existing 3D viewers currently cost £999 for the wired (HMZ-T2) and £1299 for the wireless (HMZ-T3W) models. These are running at 1280 x 720. Typically those would be the same price in dollars.
Unless Sony is planning to discontinue the 3D viewer range or the resolution of the VR sets is lower I can't see the VRs being cheaper than the 3Ds.
Instead I reckon we could see a few hundred being cut from the 3D viewers and the VRs taking their place at the $1000 price point.
Hope I'm wrong though. I'd consider paying up to $500 but the key for me (assuming the quality is everything we hope) is the weight and wearer comfort. I had an HMZ-T1 for about a month but sold it on as it gave me a headache to wear.