I picked up a Nikon 3-9x40 from Wallmart for my 10/22. It works great, and was under $150. Based on some of the reviews on AR15.com, it's a pretty good bargain. I wouldn't go any cheaper.
I put a Nikon prostaff on my bolt .223, keeps zero, and accurate while shooting. Lets more light in than my brothers leuopold! With the BDC its a bargain IMO!
I have a simmons on my mini14, I want to get rid of it.