Without going too off topic, most digital NV uses added on IR illumination, which point you might as well go B&Q and get some christmas lights and wrap them around you (unless your hunting/stalking animals which is a different conversation)
For airsoft, you can get early Gen2 devices with a tube on it's way out for about £1000. Decent stuff is starting at around £2k with the high end going up to £7k for binos and the odd chinese made quads for £10k ish