Since the "buy now" price is the same as the opening bid price, if you want that one, you can just click "buy it now" and get the best price that will be possible under the terms of that auction.
As far as the price, I've played with some lesser (up to a few hundred dollar) "night vision" monoculars... wouldn't give you a dime for any of them. Based on that, I'm assuming you will have to lay out some cash for something decent. When all else fails, I'd find out what the military uses, and using that as a baseline, find out if you want more or less functionality for your purposes. That is what the military uses, but ymmv of course.