I just checked some BOS-LAX flights in June, and it looks like I was getting only about $0.011/point, which is down from the 0.013-0.014 that were at not too long ago. I also checked a BOS-SEA flight in May, which was just under $0.012.

Obviously there is route-to-route variability, but this seems like a 20-30% devaluation of the points. I guess this is a pretty big downside to these amorphous points based plans, where they can arbitrarily devalue your points without warning.