I saw that one too! Actually it is only $5 off. It is a golf range finder, and the "reticle" appears to be a simple stadimeter type of arrangement, just like the normal BDC we all know and love. Typically, you focus on the flag which is always a set height. The lens is calibrated such that when it is in focus, the indicator tells you the correct distance. It is an old Euclidian Geometric function. Don't know the formula. If you click on the "manufacturer site" you'll get to see a lovely flash "demo" commercial and some more info.
When I first saw it, I thought it was a gun sight. I started thinking about what a rifle would look like with one of those mounted behind the sight!
But I don't think even I am that bubba.