It really depends on what you use the miles for. I tend to think RDMs are worth somewhere between 1.5-2 CPM if you are using them for award flights. They can be worth more for upgrades. I used 30,000 miles to upgrade a S fare DEN-LGA (and back) to first class. The price difference between my S fare and the HUP (the lowest F) that was available was around $1700. If you look at it that way, I got 5.6 CPM for my RDMs.