Primary Arms red dots are remarkably decent for such a low cost. Early on people had problems with some of their products being hit-or-miss, but lately they have been pretty good. I have an Aimpoint CompM2 clone that they make that I've run on a 7.62 AK for a couple years. Their Aimpoint micro clone should run for a long time on an AR or lighter rifle. I have noticed that my optic has that blue tint to the glass you see in cheaper red dots and the dot itself isn't as sharp as on an actual Aimpoint, but it works for me. Ironically, Primary Arms is an Aimpoint vendor as well on their website.
So, you might not want to trust your life to one, but they are pretty good for a range optic under $100.
Note: This optic is a couple years old and they showed signs of improving their quality since then.