I'm not so sure about the airsoft sniper rifles that are in the $300 range, since that is more than my cheap a** would spend, but I can say that for about $160 - $180 or so, you can get a UTG L96 with scope & bipod (and we are talking a GOOD scope). I have heard nothing but good things about the UTG L96, and it is a REALLY nice sniper rifle for the price IMO. Yea, it doesn't look any different than the other L96 clones (well for the most part), but it really is a great gun as far as I am concerned. I would check out pyramydair; they have one with a UTG 4x32 scope, and if you spend like $15 more, you can get one with a UTG 4x40 ILLUMINATED reticle scope. Hope this helps a little. Just my 2 cents.
Favorite airsoft rifle manufacturers: Jing Gong, Well, UTG
Airsoft Sniper Rifles