$500 is about the lowest that I've seen for a head-mount binocular NVG setup.
*link*
The big issue is that they weigh almost 2 pounds, and they will seriously hinder the ability to wear a helmet. You'll also lose your peripheral vision with them, since they only operate on a specific viewfield focus.
I didn't happen to see if they have flash suppression. That would be a big problem if they didn't because if a car or cyclist with an HID comes at you, w/o a suppression circuit you'd be hella blind.