I've got a Vortex Crossfire II 3-9 I paid less than $200 for. Of course, then you have to mount it, my P.E.P.R. mount was probably $80 or $90. But lots of decent options out there for under $200. Vortex, Bushnell and Nikon make plenty in this pricerange that are perfect for an AR. Just got back from the range sighting mine in at 100.
Vortex is always a good option. The Crossfire II is an underrated scope in my opinion. I have one in a 1-4 on my 3-gun rifle
I ran a primary Arms 1-4 for about 3 years and had no problems with it at all. It was about $200 WITH A MOUNT. Robar still uses one of them and beats me regularly with it