Late to the party on this, but I think the current best bang for the buck optic is the Sig Romeo 5.
High quality sight I?d put just a step below my Aimpoints.
They can be had for ~$120. I actually like the cr2032 battery version better than the AA battery Romeo 5X or 5XDR if you don?t need the dual retica. Its less than half the price and I have a ton of the cell batteries for other optics.
Using the low mount, it gives a true cowitness, lower 1/3 with high mount.
Best part is 50k hour battery life due to MOTAC technology.