The Nikon Prostaff is right at $150 and is the cheapest scope 's suggest. Move up to $200 and there are options far better, and well worth the extra $50. Go any cheaper than the Prostaff, and you are asking for trouble.
Right now the Vortex optics are offering the most for the dollar. Any of their Binoculars, scopes, or red dots are excellent buys. You'd have to pay $200 more to most any other company to get optics that equal what they are putting out right now. The Diamondback 3-9X40 can be had for slightly under $200 and is a great scope.
There are other good scopes. I've had good luck with, the better Nikons, and Burris. I also own Zeiss and Leupold, but for $200-$300 less money the Vortex products are awfully close.